There was this guy, who’s only job, was decide whether or not to add a second to the UTC (Universal Time Coordinated) atomic clock each year. Unfortunately this year, he thick thumbed the add button and accidentally updated the space time continuum. The theory was that “history” would change if people from the future travelled to the past, but there is a constant in evil that has persisted since Adam and Eve. When the leaders from the present time were exchanged with the leaders from the past, it did not effect the constant in evil. What did change is that the evil people leading the world were exposed by anyone with something as simple as a history book. They are no longer able to hide so easily.
Anyway, the part of the world where people from around the globe come to fight (Europe, the Middle East, and North Africa) split into 734 kingdoms due to the technological failures that made centralized power over long distances virtually impossible for the time being.