This is a bit of a mystery. The Hittite Empire fell, "Sea Peoples" apparently invaded Egypt, and several cities were apparently ruined, but what exactly happened? It's tough to make an alternate history if ours is fuzzy to begin with.
Unfortunately, events that happened thousands of years ago are poorly remembered, with few documents remaining, and writing was a profession in the early ages of civilization, so it was not as widespread back then as it is now.
Might the fall of the Bronze Age, and the dawn of the Iron Age, in the Mediterranean area, have been the handiwork of some forgotten Genghis Khan or Attila the Hun type?