What An Idiot / Harry Potter and the Goblet of Fire

• In the prologue, Voldemort and Pettigrew are hiding in the former's family manor in Little Hangleton.
  You'd Expect: They would set up protective spells around the place in order to detect any possible intruders, such as the one that Hogwarts has that makes the place look still abandoned.
  Instead: They don't, and simply lounge in one of its chambers, lighting a fire that can be seen from outside.
  As a Result: Frank Bryce, an old Muggle, is able to sneak up on them and hear part of their talk. This proves to be inconsequential because Nagini casually finds him and warns Voldemort and Pettigrew, and they kill Bryce. But this only shows how easy it would have been for a spy or a tracker under an Invisibility Cloak to catch the dark wizards.
• After the madness of the Quidditch World Cup, riots and all, Ron and Harry come back to the Burrow to find that Mrs. Weasley has purchased dress robes in addition to their usual books and quills. Ron is furious that she's gotten him outdated maroon robes with lacy sleeves, while Harry feels guilty that he has gotten nice ones since Mrs. Weasley used money from his Gringotts vault.
  You'd Expect: Even though Ron has his pride, Harry at some point would buy him new dress robes that are in style, not maroon, and much nicer, and give them anonymously, or give them to him as an early Christmas present so it won't seem like charity.
  Alternatively: Ron could swallow his pride and ask Harry for some money/new dress robes, or Mrs. Weasley could just ask Harry to loan her some money and offer to pay him back later. That way, when special events come up, Ron won't look like a fool in his clothes.
  Or: They ask Hermione to help transfigure the robes. It shouldn't be difficult to change a robe's colour or remove the lace for a genius prodigy witch.
  Or: If Ron is too proud to ask Hermione (since he starts grappling with his romantic feelings for her in this book), he could ask a teacher. McGonagall or Flitwick would surely be able to alter the robes and are nice enough to be discreet and not embarrass Ron about it.
  Instead: No-one does any of the above, although Harry does buy lots of socks for Dobby as a present, and at the end of the book asks Fred and George to buy Ron new dress robes on his behalf.
  As A Result: Ron goes to the Yule Ball in those robes, and that's only the first of many catastrophes that ensue that evening.
• Rita Skeeter is a troublemaking journalist. Her goal is to smear as many people as possible and create drama, so as to pay for her Unlimited Wardrobe and manicures. While half of her stories have a kernel of necessary truth, like her stuff about the disappearance (and as it turns out, murder) of Bertha Jorkins, it's obvious that she doesn't care about telling readers the truth.
  You'd Expect: People would eventually learn to take her articles with a grain of salt.
  Instead: She is blindly believed over and over. She even manages to convince Molly Weasley that Hermione has been dating and cheating on Harry, when Molly should really know Hermione well enough to realize that there isn't an iota of truth to this.
  You'd Also Expect: That someone would have filed a lawsuit or sent a cease and desist letter for libel, especially parents of children who get harassed as a result of her stories. (Especially since this is Britain, which in the Muggle world has positively draconian libel laws.) Or they would challenge her to a duel in public and humiliate her. Really, considering that Rita basically fabricates entire interviews and openly insults people in her articles, it's a miracle that nobody has tried to take revenge on her (with a career like hers, you would think she needs to be surrounded by bodyguards 24/7).
  Instead: Dumbledore is the only sensible person who bans Rita from Hogwarts after her libelous interview of Harry Potter, while everyone else laps her articles up and nobody ever seems to care how many people she's blatantly lied about.
  The Result: Rita goes unchecked, even harassing Hermione, a minor, for insulting her. Her articles also end up convincing Cornelius Fudge that Harry is a lying attention-seeker, leading to Fudge's year of idiotic decisions in ignoring Voldemort's return.
• Voldemort and Barty Crouch Jr. intend to restore the former to a physical body via a ritual that requires Harry's blood to work. To acquire this ingredient, the villains hatch a plan to have Crouch Jr. use Polyjuice Potion to disguise himself as Mad-Eye Moody, Hogwarts's Defense against the Dark Arts teacher for this year, before using a Portkey to spirit Harry away from the school and Dumbledore's protection, and send him to Little Hangleton, the location for the ritual.
  You'd Expect: Crouch Jr. to invite Harry into his office and Portkey him to Little Hangleton from there, or in case this is not possible due to Hogwarts' barriers, simply stun Harry and throw him in Moody's magic chest to take him to the town. This could be done at any point in the school year and it would be hours before anyone realized Harry was missing.
  Alternatively: The resurrection spell requires the enemy's blood be "forcibly taken". Depending on how loosely those constraints can be interpreted, Harry doesn't necessarily need to even be aware that his blood is being stolen, much less be present for the ritual it's intended for. Crouch could find some pretense to "accidentally" cut Harry, apologize, then send him off to Madam Pomfrey while wiping up his blood in a vial for the ritual. Giving him private dueling lessons, for example, as his Defense professor. Voldemort can kill Harry later after he is resurrected.
  Instead: Crouch Jr. hatches an incredibly convoluted plan to enter Harry into the Triwizard Tournament as a surprise fourth contestant, even though only three students are supposed to compete in the tournament, then make Harry win the entire tournament against the best contestants of Europe, then turn the Triwizard Cup into a Portkey and arrange for Harry to grab it in the last moments of the tournament.
  Result: This requires Crouch Jr. to basically hand-hold Harry through the entire tournament while also maintaining his cover for an extended period, exponentially increasing the number of things that may go wrong.
• Despite Harry not applying for participation in the Triwizard Tournament, his name still comes up. The only explanation they have is that someone tampered with the Goblet of Fire, and it definitely wasn't Harry because that would be far beyond his skill. Someone is setting him up. However, when it is quite reasonably suggested that Harry should be excluded, the answer is that it's impossible because — as was mentioned before the start of the application period — those who are selected by the Goblet are entered into a magical contract and have to participate in the Tournament.
  You'd Expect: That the precise details of this contract would be immediately made clear and any possible loopholes would be exploited, or at the very least explored. For example, Harry could do nothing and disqualify himself, or given that contestants are not allowed to ask teachers for help, he could try exactly that. There are a lot of people who are unhappy with this development, starting from Harry himself, and then to his friends and the supporters of the legitimate Hogwarts champion Cedric Diggory, and the delegations of the competing schools. All of them would no doubt be satisfied if the teachers and Harry just came out and said, due to obvious tampering with the Goblet, Harry would deliberately fail every task in the interest of fairness even if he wasn't responsible for the sabotage.
  You'd Also Expect: That the adults would try to find out the culprit, since they're positive that Harry could not have done this on his own. After all, if they let Harry participate, they are essentially being played by whoever set Harry up in the first place.
  Instead: Nobody does anything, and the fact that Harry's participation was orchestrated is completely ignored. Everyone takes Crouch Sr.'s word that Harry has no choice but to enter at face value, unaware that Crouch Sr. is under the Imperius Curse and is being forced to spew out lies. There's no investigation, and even when the final task comes — so whatever the culprit's intention was, this is their last chance to act upon it — no one is keeping an eye on the participants.
  As A Result: Crouch Jr. has free rein to rather blatantly interfere with the task and ensure the completion of his evil plan, culminating in the death of Cedric and the permanent tarnishing of the Triwizard Tournament's reputation.
  Moreover: The second and third tasks are a rather baffling moment for the entire school, because even setting aside the suspicious circumstances surrounding Harry's participation, somehow none of the hundreds of people present saw it as odd that during the grand events of the Tournament other than the first task, nobody gets to see the contestants.
• Hermione first learns of the Hogwarts house elves during this book. She isn't happy when she finds out that the elves work without pay, sick leave, or pensions, and decides to set up the Society for the Promotion of Elfish Welfare (S.P.E.W.) to try and improve things for them.
  You'd Expect: If Hermione is serious about fighting for house elves' rights, she'd look for cases of elves who had genuinely suffered abuse and mistreatment from their masters and/or the Ministry (e.g. Dobby, Hokey, Kreacher and the elves of the Black family, etc.) and base her arguments around them. She did just that in the previous book when she was helping Hagrid to research for his defense of Buckbeak the Hippogriff.
  You'd Also Expect: Hermione would talk to the house elves and ask what they would want as a better lot in life. House elves run under Blue-and-Orange Morality where they genuinely prefer to work for witches and wizards and only hate abusive masters or ones that dismiss them. It becomes a White Man's Burden if you want to speak for an oppressed group, and you don't bother to find out what the oppressed group wants.
  And, as a bonus: She would also choose a name for her crusade that doesn't sound so stupid and utterly impossible to take seriously.
  Instead: She only uses the Hogwarts house elves as an example of why elves need rights for SPEW. Elves who, despite not being paid for their work, are quite content with their lot in life.
  Result: No one takes Hermione's case seriously, while the Hogwarts house elves become disgusted with the Gryffindors. It starts when Hermione asks why they cover a drunk Winky with a blanket, instead of cheering her up for getting fired and then learning her former master, Barty Crouch Sr., is ill. Then Hermione starts knitting hats, in the hopes of freeing the house elves, only for Dobby to pocket them because the other elves view it as a distasteful gesture. It means he has to clean Gryffindor tower on his own, which is unfair even if he doesn't mind.
• Barty Crouch Jr. is using Polyjuice Potion to assume the identity of Mad-Eye Moody, this year's Defence Against the Dark Arts teacher. In order to maintain his disguise, he needs to drink a fresh dose every hour.
  You'd Think: Since he already knows how long he has to stay at Hogwarts and can do basic arithmetic, he'd come prepared with all the doses he needs for the year squirreled away in his bottomless trunk or somewhere else (and possibly a little surplus, just in case).
  Or At Least: If he runs short and needs a mid-year resupply, he'd simply contact a Death Eater on the outside (such as Wormtail) and have them nip down to Knockturn Alley and buy him some, or just pop out himself on a weekend on some pretense.
  Instead: He steals the ingredients necessary to brew a fresh batch from Snape's inventory of ingredient storage, despite the fact that this would be very likely to advertise to anyone who finds out that somebody is brewing Polyjuice Potion.
  Result: Snape busts him at one point, and Crouch Jr. pulls a Bavarian Fire Drill that Dumbledore ordered him to search Snape's office. The only thing that saves Crouch Jr. from having to duck a school-wide manhunt is Snape blaming Harry Potter for the theft because of both his hatred for the kid, and the fact that some of Harry's possessions coincidentally ended up near the scene of the crime — and Harry himself only fails to dispute this because Snape failed to specify the timeframe when accusing him, making him think this was about two years ago, when Harry and his friends did steal these ingredients.
  You'd Also Expect: Snape would find Crouch Jr.'s story suspicious, and ask Dumbledore whether he really did tell Moody to search his office. After all, Snape is aware that Dumbledore trusts him implicitly, and would be very unlikely to order something like this. Dumbledore could then confirm that he didn't order Moody to do anything of the sort, and discover that he is an impostor after investigating this lie.
  Instead: Snape apparently just shrugs and accepts Crouch Jr.'s story.
  The Result: Dumbledore doesn't figure out that Moody is an impostor until too late, and Voldemort is resurrected.
• Harry figures out that for the second task of the Triwizard Tournament, he and the other three champions must find a way of breathing underwater for at least an hour, swim to the bottom of the Hogwarts lake, and retrieve something precious to them within an hour-long time limit. They are warned that should they fail to retrieve their object, it will be lost forever. Upon reaching the lake's bottom, Harry learns that the "precious things" are people the champions are close to.
  You'd Expect: Harry to figure out that the warning's just for show; none of the officials in charge of the Tournament would let any of the hostages die, given the safety measures that have been put in place for the Tournament, and the fact that all the hostages are actual people.
  Instead: Harry takes the warning seriously, and after freeing his hostage, wastes time waiting for the other champions to show up and rescue their hostages.
  As A Result: Harry nearly drowns and ultimately finishes second-to-last after one of the other champions was eliminated early. Fortunately, Harry's determination to make sure all the hostages are saved is seen as him showing moral fibre, and he subsequently gets boosted to second place in the tournament ranking.
• With that said, there is the dubious means of using actual underage students as part of the Second Task. The tournament regulations set it so that only seventeen-year old witches and wizards could compete. In turn, all of the people chosen as hostages are underage; Cho Chang at the oldest is fifteen or sixteen.
  You'd Expect: Considering the first task had the champions retrieving golden dragon eggs instead of real ones, that the hostages would only be effigies or sculptures, with the real ones safe and above the water, and in view of their champions and family. Madame Maxime has already questioned that Dumbledore might have messed up the aging line; the spell works in that the hostages will stay asleep and breathing, not waking up, until they surface.
  Instead: They use actual hostages. One of whom actually happens to be an eight-year old girl, Fleur's sister Gabrielle. In a lake which is miles deep; if the hostages happened to surface in a deep part of the lake and don't know how to swim, they could drown. The merpeople also have been given instructions that if a champion tries to rescue multiple hostages, that they will restrain them, unless one has the presence of mind to threaten them with a wand and scare them, as Harry does.
  The Result: While no one gets hurt, apart from Fleur getting attacked by grindylows, the family members of the hostages understandably panic with the children being asleep underwater. A terrified Percy sprints to Ron and drags him out of the water, and a hysterical Fleur refuses to get medical attention until she finds out that her sister is safe. And no one points out that if a champion fails to reach their hostage, the merpeople would have to wait for an unknown signal to cut their hostage loose and take them to the surface, long after an hour.
• During the lull between Voldemort's defeat and the Longbottoms being tortured, Crouch Sr. is trying to ferret out remaining Death Eaters. Ludovic Bagman, then a star Quidditch player, is one of the accused as allegedly a part of Rookwood's spy network. The Wizengamot like Bagman for his performance and are squeeing to see him in court while believing in his innocence. Crouch Sr. believes he is guilty and presses the charges accordingly. In a rare case where they disagree, Moody says during the trial that Bagman isn't evil. He proclaims that the "boy" is an idiot and has always been dim so he's probably innocent of the charges. Bagman himself admits this in Sincerity Mode that he is not the brightest bulb in the shed.
  You'd Expect: Crouch Sr. would have compiled his evidence better so as to sway the Wizengamot and break that pedestal.
  Instead: He merely lays the charges and recommends the sentence immediately before anyone can give their testimony, prosecution, or defense.
  The Result: You know it's bad when Mad-Eye Moody presumes innocence in a suspect rather than being his paranoid self. The Wizengamot yells at Crouch Sr. for the accusations before he can finish his recommended sentencing, and thank Bagman for his excellent Quidditch performance. This gives time for Bagman to explain what actually happened: he thought Rookwood was recruiting him for the Ministry, promising Bagman a job when the latter finally retired from Quidditch, and had no idea the man was a Death Eater who set up a spy network. No one votes Bagman guilty, and no one has accused him ever since. Yes, he does get that Ministry job.
• Sirius Black describes to Harry how Barty Crouch, Sr. fell from grace. Shortly after Voldemort's downfall, while Crouch Sr. was head of the Department of Magical Law Enforcement, his son, Barty Crouch Jr., was arrested with a group of Death Eaters, composed of Sirius's cousin Bellatrix Lestrange, her husband, and his brother, after the Lestranges captured and tortured the Longbottoms with the Cruciatus Curse, leaving them legally insane. The crime caused massive public outrage because the Longbottoms were popular, and Neville was considered the other potential Chosen One. The Longbottoms were in no condition to provide testimony, and their son Neville was only a baby; on the other hand, the Wizarding World wanted blood and to see the criminals punished. Mrs. Crouch, who was dying from a terminal illness, in particular was in hysterics about her son being arrested, because he was their only child. And Crouch Sr., as Sirius describes him, cared very deeply about his reputation above all else and was ruthless to a point many considered him to be not all that different from Voldemort. He was also a shoo-in that many considered was guaranteed to succeed Millicent Bagnold as Minister for Magic after her retirement.
  You'd Expect: That Crouch Sr. would do all that he could to verify his son's innocence or guilt. The Ministry has Veritaserum, Time Turners locked in the Department of Mysteries, and the means of extracting Crouch Jr.'s memories via Pensieve or Legilimency. Using these methods to get the truth out would do wonders at establishing beyond a reasonable doubt what Crouch Jr's involvement (if any) was.
  And: Crouch to do what most Muggle courts require when there's an obvious conflict of interest, and recuse himself.
  Instead: Crouch doesn't want to give the impression that he plays favorites, and grants his son a trial with a Kangaroo Court instead. Crouch Jr. spends the trial begging for his life and fighting the Dementors; his mother faints while watching the courtroom antics.
  As A Result: The entire Wizengamot votes to send the Lestranges and Crouch Jr. to Azkaban for life. While the Lestranges absolutely were guilty of the crime, Crouch Sr. ends up destroying his reputation and chances of becoming Minister for Magic. The Minister's job goes to Cornelius Fudge, while Crouch Sr. gets reassigned to heading the Department of International Magical Cooperation. The public are left questioning how the greatest fighter of Death Eaters failed to notice that his own son was going astray, and conclude he either practiced Parental Neglect at best, or was an abusive father at worst.
  To Make Matters Worse: It doesn't help when, as a last wish to his dying wife, Crouch Sr. smuggles her into Azkaban so that she switches places with her son; otherwise, they would have both died, Crouch Jr. to the Dementor's Kiss, and Mrs. Crouch to her terminal illness. Then he proceeds to use the Imperius Curse to place Crouch Jr. under house arrest for the next decade, and also subjects Bertha Jorkins to a powerful Memory Charm that leaves her brain-damaged when she finds out the truth.
  Result: While it is unclear whether Crouch Jr. was a sincere Death Eater before Azkaban or just an unwitting associate of them, he definitely is a full-fledged Death Eater when he gets out. He seizes the chance of freedom when Voldemort finds out about him from Jorkins, and helps bring Voldemort back to power. Nice Job Breaking It, Hero doesn't begin to cover it.
• For the third task, Crouch Jr. is one of the teachers that is patrolling the maze. His goal is to get Harry to the cup, alone. He manages to incapacitate Fleur by stunning her, using Moody's magical eye to see through the hedges.
  You'd Expect: He would do the same to Cedric and Krum, or put another jinx on them that quickly incapacitates them.
  Instead: Crouch Jr. uses the Imperius Curse to force Krum to use the Cruciatus Curse on Cedric. Note that while the Cruciatus Curse can break a person's mind, it does not work quickly. Its entire point is to make a victim suffer To the Pain. Harry overhears Krum cursing Cedric and his Chronic Hero Syndrome takes over, where he tears through the hedge and stuns Krum, saving Cedric's life.
  The Result: Cedric makes it to the center of the maze at the same time Harry does, and they team up against an Acromantula that would have tackled Cedric if Harry hadn't shouted in warning. Neither Harry nor Cedric want to take the cup and claim the champion title after realizing that they've helped each other through the tournament, so they agree to take it together. This leads to Cedric dying by Voldemort and Pettigrew's hand, and possibly to Amos Diggory being one of the few Ministry officials who believes Harry about what happened.
• The cup has turned out to be a portkey that has transported Harry and Cedric to a graveyard. There is no one immediately present and the cup is in close range.
  You'd Expect: Harry and Cedric to grab the cup again. If it takes them back to Hogwarts (which is what happens), then the trip to the graveyard wasn't likely a part of the challenge. After this, they could tell everyone what happened and the Aurors would be able to investigate. In any case, especially in case it might be after all some kind of twisted new challenge, they should be completely on guard.
  Instead: They waste time taking in their surroundings and waiting for something to happen.
  As a Result: Peter Pettigrew and Voldemort turn up, which incapacitates Harry due to his scar, and then kill Cedric, who was standing around doing nothing. Pettigrew then carries out the ritual to restore Voldemort to power.
• Related to the above...
  You'd Expect: Crouch Jr would remove the original Portus spell on the Cup, meaning that it will only take the user to the graveyard. This would leave Harry with no way out and allow Voldemort to take his time to announce his return and Harry's downfall.
  Instead: He leaves the original Portus spell on the cup, apparently doubtful that Harry would be able to use it to escape.
  As a Result: Through admittedly unexpected circumstances, Harry escapes. While Fudge doesn't believe that Voldemort's back (in a series of What an Idiot moments listed below), Voldemort misses the perfect chance to kill his nemesis.
• After Voldemort is resurrected, he, Harry, and the Death Eaters are all in a distant place, the only possible witness has been killed, and Harry is tied to a gravestone, completely at Voldemort's mercy.
  You'd Expect: That once Voldemort had gathered his Death Eaters, he'd kill the restrained Harry. If he wants to prove to his followers that his failure to kill the kid 13 years ago was a fluke, a simple use of the Killing Curse should be sufficient.
  Instead: He lets his ego gets the better of him, and frees Harry before challenging him to a wizard duel so that he can rub it in how superior he is. And instead of finishing him off right away, Voldemort uses the Imperius and Cruciatus Curses on Harry to taunt him, and finds out that thanks to his spy, Harry was taught to resist the former. Granted, he couldn't have known that this particular combination would result in Priori Incantatem happening, but Harry still ends up with plenty of leeway to escape without it (imagine if Harry had used a summoning charm to try and grab the Triwizard Cup earlier than he actually did).
  The Result: Harry is able to escape, embarrassing Voldemort in front of the cronies he was trying to impress, and he warns Dumbledore and the world about Voldemort's return.
• Harry is back at Hogwarts, clinging to Cedric's body and repeating to Dumbledore that Voldemort is back. Crouch Jr. is baffled that Harry is alive, since he assumed that Voldemort would kill Harry immediately as soon as he was resurrected. Dumbledore has ordered Harry to stay in his sight while he has to talk to the Diggorys about their son's mysterious death. Crouch Jr. overhears this while offering to take Harry away from the traumatic site.
  You'd Expect: Crouch Jr. would stand by, and wait for Voldemort to send him a message about what to do next. His cover is so deep that Dumbledore hasn't suspected him for an entire year.
  Instead: He forcibly leads an injured Harry away to his office to interrogate him about what happened in the graveyard, and what happened to the cowardly Death Eaters that returned to the Dark Lord. Then he wastes time Evil Gloating and ends with how he plans to kill Harry, so that Voldemort will reward him. Crouch Jr. missed the memo that Voldemort wants to kill Harry personally.
  The Result: His strange actions alert Dumbledore that this is an impostor, and the monologuing gives them time to arrive. He, McGonagall, and Snape rescue Harry in time, Stun Crouch Jr., and expose him. Dumbledore then ties up Crouch Jr. while the latter is hopped up on Veritaserum, and gets Madam Pomfrey to help the real Moody, who was locked up in his own trunk, Stunned and starving.
• Not long later, Minister for Magic Cornelius Fudge is informed of this turn of events. The evidence to support this includes the news coming from Albus Dumbledore, who isn't known for making stuff this serious up, and two testimonies. One of these is from a Death Eater who has admitted under Veritaserum that he has been in contact with Voldemort and working to ensure his return, and the other is from Harry, who claims to have seen first-hand the ceremony that restored Voldemort to full power, and has the injuries to show it. Dumbledore has ordered Professor McGonagall to stand watch over a bound Crouch Jr., who is pliable for interrogation, and to notify the Minister in case he wants to question Crouch Jr.
  You'd Expect: Fudge to realize that a bound and disarmed Death Eater would be unable to hurt him personally.
  Or: If he was really worried about his safety, he would bring some Aurors or other Ministry officials for the interrogation.
  Instead: Without Dumbledore's permission, he brings a Dementor along with him to the interrogation. Dementors are known to hate the victims who escape them, and Crouch Jr. escaped them from Azkaban. They also tried to give Harry the Dementor's Kiss merely for defending Sirius the previous year.
  The Result: Before Fudge can so much as ask a question, the Dementor swoops on Crouch Jr. and gives him the Kiss, destroying his soul and his ability to testify. To make matters worse, Fudge goes Never My Fault by claiming that Crouch Jr. was an unreliable witness due to being a "lunatic". Professor McGonagall is obviously furious, and Dumbledore has to emphasize that Fudge tampered with a witness because of his own ego.
• As well as the above evidence, Snape shows Fudge a very clear Dark Mark on his arm. The last time it was easily visible was during Voldemort's reign of terror. And, of course, Cedric Diggory's dead body.
  You'd Expect: Fudge to figure out that with all this evidence supporting it, it's quite likely that Voldemort's really back, and then take the actions suggested by Dumbledore to prevent him getting power and resources. Even if Fudge personally doesn't believe it, he should still try and have the matter investigated to confirm it for himself, and he can always order it to be done discreetly in order not to cause a social panic. He's certainly an egotistical man, but by that reason he should know he has a lot to gain, politically speaking, by putting all his effort on managing the situation of Voldemort's return (and everything to lose if Voldemort's return happens to be true and Fudge doesn't act on it).
  Instead: Not only does Fudge take no appropriate measures, he somehow gets it into his head that Dumbledore's making all this up to try and take Fudge's place as Minister — nevermind that Dumbledore has never wanted the Minister's post as far as Fudge has known him — all because he doesn't want to deal with Voldemort's return.
  As A Result: Voldemort's side is able to operate quite freely, recruit the giants to their cause, and break out a load of their supporters from Azkaban, while Fudge does absolutely nothing useful. Thankfully, Voldemort doesn't choose to focus all his efforts on taking over, but if he had, the situation could have become a lot worse. And when the truth does get out, the unanimous outcry from the wizarding community forces Fudge to resign and destroys his career.
  Even Worse: The majority of the Ministry of Magic follows blindly Fudge's politics, being either that submissive to his authority or just apathetic to the topic, or maybe buying into his mindset of simply not wanting to accept it. Even the Auror Office, whose members should be naturally wary to dismiss like that the possibility of Voldemort having recovered his power, don't seem to make any objection. The only people in the Ministry who believe Dumbledore are those who are already his allies, who are few and not excessively powerful.
• Related to the above, Fudge is refusing to believe that Voldemort's returned.
  You'd Expect: Dumbledore would immediately use a Pensieve to review Harry's memories of the event and show them directly to Fudge, or view them himself in order to ascertain exactly what happened and gain information. Granted, memories can be altered (and Harry tells him), but Harry doesn't know how to do that, there hasn't been sufficient time for him or anybody else to do so, and it's not just Voldemort's return, but he's an eyewitness account into investigating the death (murder) of another student (Cedric) during the Triwizard tournament. Not to mention that, when an explicitly doctored memory is shown two books later, the signs of tampering are rather obvious even to the untrained eye despite having been done by an expert. Even someone as dense as Fudge would have a hard time claiming Harry imagined the whole event right down to the very minute details like the real-life cemetery he'd never been to (something easily verifiable since Dumbledore knows all about Riddle's origins).
  In addition: Taking Pensieves would also mean Dumbledore has a preserved record of Crouch Jr.'s entire confession, which he could then use to confront Fudge with ironclad proof that is impossible for him to dismiss without looking like a coward, moron, or fifth columnist.
  Alternately: Dumbledore could just use a Time Turner to take Fudge back in time to the cemetery under an Invisibility Cloak to show him the evidence of the ritual to his own face.
  Instead: Nobody thinks to use this evidence, and it doesn't help against the stigma that occurs against Harry and Dumbledore in the next book.