Clyde spent 10 years planning every detail of his rampage, taking into account everything from obscure legal precedents to the probable funeral arrangements of Nick's understudy. The only thing he missed? Mere days before the plot, after he stopped researching and plotting, the understudy ditches her old man and gets a new one, who has the ability to blow the cover provided by his Panama corporation.
More Fridge Brilliance: Clyde said that he was going to "bring down the temple" and that it will be "biblical". He hinted of his own death, just like Samson, which was part of his plan.
A Blink And You'll Miss It — When Clyde is talking to Nick outside the prison, he says "This is Von Clausewitz shit — total fucking war". This is in reference to Von Clausewitz's "Third Reciprocal Action", which basically says that to defeat an enemy, you must completely annihilate them. That is why he wants to kill everyone in the Justice Department, and explains his targeting of the city hall meeting at the end.
Clyde offering his cellmate half of his expensive lunch. An act of friendship? No, he was giving him a last meal before his execution.
Clyde's claim that he would've accepted a not guilty verdict on Darby and Ames' trial might have more validity than one would think. Keep in mind the only reason Clyde got caught in the first place was because he allowed himself to be. If Darby and Ames got off with a not guilty verdict, Clyde could've covertly killed both of them in his own time and he wouldn't have felt wronged by Nick because he did his best. Meaning he would have his revenge and sense of fulfillment without having to wage a war against the system.
Why did Clyde purposefully get his bail denied? Because there's a good chance he would be put under house arrest even if he was bailed out. So by staying in prison his sneaking in and out to continue his vendetta would go unnoticed.
Nick insists that the system works, even though he literally let a violent criminal go, just so he could keep a track record going. Did he buy his way through law school or something? Compounding this is that letting a child murderer plea out would destroy any career he might have had as a DA.
Nick is an idiotic slimeball. Bribing his way through law school would not be out of character for him.
There’s actually a great deal of Truth in Television to it. In many areas, promotion is based on successful trial rates, which encourages lawyers like Nick to only go after sure things and plea bargain anything with uncertainty in order to inflate their success rate and get promoted.
Clyde brings this up at more than one point in the movie; it finally sticks near the end. The fact that Nick didn't care or even tried to prosecute Darby is what ultimately kicks off the plot. The point of it all was to make Nick care about more than just his own career. The Justice System only works if the people in it not only follow the letter, but the spirit of the law. Nick didn't.
Nick’s Xanatos Gambit at the end raises a couple questions. Namely, how did he know Clyde would return to his cell? Clyde had already been released due to their previous deal, he had no reason to return to prison. On that note, why did Clyde return to his cell? Couldn’t he have just skipped town and detonated the bomb remotely? With all that in mind, how did Nick know Clyde would return to that particular cell? Clyde had tunnels dug into every cell, if he was going back to prison to hide, wouldn’t it have been smarter to hide in a different cell?
1) Clyde hadn’t been released at all and was officially still imprisoned because Nick didn’t take that deal. 2) He returned to his cell on the assumption that his alibi for the continuing murders, that he was “safely imprisoned” was still intact, and not being in his cell would scuttle his alibi. 3) Nick knew Clyde would return to that particular cell because it’s the cell he’s officially being held in and him being in a different cell than that one would reveal that he can leave his cell. The only reason Clyde had tunnels into every solitary cell was because he had no foreknowledge of which cell he’d be placed in.
