You can argue the realism that blockbuster cinema turned into in the mid-naughties was inevitable. The garish films of the nineties had made jovial jaunts incredibly uncool and film needed to go in another direction, but there's no way that the 9/11 attacks didn't play a central part of it. Look at the films that came out pre-9/11 that attempted to offset the likes of Batman And Robin; X-Men and Spider-Man both feel incredibly light in tone and content by modern context. The two films that made realism vogue have strong links to the attacks; Casino Royale's villain is using his poker winnings to fund terrorism, while The Dark Knight looks at unexpected metropolitan destruction. There's the usual 9/11-style to things (just look at that image of Batman stood in the ruins of a destroyed building), but there's an attempt to use it to make previously removed characters part of our own world. Heck, The Joker's speech about events being "all part of the plan" is essentially an explanation of just what made the destruction of the World Trade Center so shocking. The world had seen real terror at home. Movies didn't need to go to crazy lengths to create major threat anymore and given how shook up the world was audiences didn't want that either.
