The entire event was triggered by a Tragic Villain with Hate Plague powers who gains sustenance whenever superheroes start in-fighting and wants the superheroes to unite to make Earth a better place.
Said supervillain was also responsible for both Civil War events, Avengers vs X-Men, Inhumans vs. X-Men, and God knows how many other massive "Hero vs. Hero" events. Because let's face it, that's the only explanation I can take at this point for why these events keep happening every few years and why people are guaranteed to hold the Idiot Ball during each one.Ironicly Chris Claremont planned for the Shadow King to be the reason why so many people in the Marvel Universe hate mutants.
