While all faction themes in V are based on the ethnic music of the corresponding civilisation, some of it also has elements whose meaning is not obvious - at first.
The Ottomans' war theme, Ceddin deden, has several snippets of Mozart closer to the end. One would find that somewhat surprising, until one realises where exactly did that cue come from: Rondo Alla Turca.
The Dutch war theme, ostensibly based on the classical Dutch folk song In naam van Oranje, is notably ominous and military-sounding, similar to the Imperial March in some ways. Why? Because the Netherlands in V is led by William of Orange - known in his homeland as the "Father of the Fatherland" - or, in Dutch, Vader des Vaderlands.
Attila from V speaks a very broken Chuvash, which might sound frustrating for those who prefer the leaders speaking their respective languages fluently. But it also shows that the Huns didn't speak Chuvash, but a language whose closest living relative is presumably Chuvash.
Since Civ 5, the Indian AI is often programmed to build a lot of nuclear weapons. India is one of the few known countries to have an active nuclear weapons program. However, the AI is designed to be relatively peaceful. This also reflect in India's real life foreign policy of dedication to world peace, but have nuclear weapons as means deterrence of any possible wars (particularly with their rivals, China and Pakistan). Even more brilliance in that its a Genius Bonus for anybody who actually learn about Gandhi beyond his popular reputation among the general populace: Gandhi admitted that if India had an arsenal of nuclear bombs, they would have no hesitation in using it against the British in a violent revolution to gain independence should things escalate to that point.
In V, all city-states hold elections. Which implies that all city-states are democracies. Not only that, but they hold elections every few turns rather than after an amount of years, so you can almost picture how their democracy evolves throughout the game: one succession staying in for centuries early on with votes on which dynasty to replace them, increasingly shifting to more regular and frequent changes of authority until, by the 1900s or so, they effectively have fixed-term governmental periods - like many modern countries.
The choice of leaders for Greece in VI - Queen Gorgo in particular - might seem like a simple attempt to make the leaders more diverse and add more female representation. That is, until you realise that she leads Sparta: her husband, Leonidas, is probably fighting in the frontlines as part of one of your military units, while she manages the country - as Spartan women did historically.
Why does the game award a cultural, scientific, religious, or diplomatic victory to someone who is about to get wiped out by another civilization's armies? Because all of these victories actually render that military victory pointless or, in the case of one, may actively be able to stop it.
A science victory results in you sending a colony ship off to another world, so now nothing that happens on this planet really matters to you anymore, as your civilization will still survive elsewhere where your enemies can't follow (or follow youmuch later)
Cultural victory and Religious victory are essentially the same here. while it may be true that your civ is about to be wiped out, all the other civs are either worshiping your gods or following your culture. Thus, with cultural victory, your culture will be remembered for ages to come even after it had fallen. With Religion, your religion will have significant influence even if their founders was gone. It might even get adopted by the Empire conquering you a la Rome with Christianity. Either way, your legacy has changed the world and will last for long after your civilization has fallen.
Diplomatic victory may actually be able to stop the conflict. It essentially means that the other civs in the game and the city states have declared you the ruler of the world. Now imagine all of those civs giving the civ about to wipe you out a call and saying that if they don't pull their armies back now, they will have to fight all of them as well. Unless the conqueror in question has already crushed those other civs into borderline or actual irrelevance, that is a coalition they are unlikely to beat, so they would have little choice but to comply.
A lot of the World Leader's rather Jerkass behaviour - refusing to get into wars that you couldn't win anyway, demanding great trade deals, and becoming war-aggressive if you have something they want - is not unlike how world leaders really do behave.
In V, the preferred ideology for the Mayans is Order. Huh.
In the same vein, razing cities becomes quietly horrifying when you consider doing so doesn't produce refugees. No Workers, Settlers or any other "civilian" units are produced, and your own population doesn't swell from occupied peoples fleeing the burning city. It just gets smaller and smaller until there's nothing but a tiny City Ruins graphic left on the tile. So where do all the people go? You slaughtered them all, of course. Tens, maybe hundreds of thousands of people, and you wiped them all out along with every building in their city. Check out the Sacking of Bukhara, the Rape of Nanjing, or the Destruction of Kalisz on The Other Wiki sometime. That's pretty much what you're doing.
Worse, Civilization V practically encourages this behavior thanks to all the semi-permanent penalties you can incur from trying to hold on to captured cities instead of razing them and resettling the land they used to occupy. Those penalties are supposed to discourage warmongering and give you a reason to liberate your cities later on, but many players see that as defeating the whole point of conquest and making your opponent stronger for when they inevitably attack you again. As a result, those players, if they go to war at all, go full genocide.
In Civ IV sometimes there actually are survivors-in the form of partisans who spawn new military units near the ruins of their home. Congratulations you just reduced one of your enemy's cities to a bunch of bitter vengeance-seeking soldiers.
Additionally, destroying a city also destroys all world wonders present within it and nobody else can rebuild them. The same is true if the city is a holy city for a major world religion. If you raze a city that is home to a large number of world wonders and/or the seat of a major faith, you are not only committing genocide but destroying culture as well.
In III, IV, and V, when you research the technology that reveals Uranium on the map, and a large cache appears right under a farm, leaving you to wonder just how long your citizens have been eating irradiated food.
Even worse is when the uranium appears right beneath one of your own cities...
Especially if that city is the centre of world tourism.
On the other hand, Uranium as you can find it in the ground has a half-life time of four and half a billion years, so the generated radiation is probably barely noticable with instruments, let alone without.
In Civilization II, one of the wonders you can build is the SETI Program. The short film that plays when you complete it shows two grey aliens at the end. They are the exact same design as the sectoids from the original X-COM!
And as of Civ V, you can build XCOM squads...
In VI, Abraham Lincoln's leader ability causes Industrial Zones to generate positive loyalty but plantations to generate negative loyalty. The implication is that Civ VI's plantations are run using slave labor, even in the Modern Era and beyond, as this loyalty penalty never goes away.
