Ff7 rebirth (crackpot) theory. Maybe spoilers?

So after playing through the majority of the game, ive yet to see it clarified or mentioned, so i started headcannoning. Do they ever mention why the gi and the cetra didnt get along? Is it because the gi brought jenova with them? Like they were escaping their own planet that had been infected, landed in the north crater and were asking for help. The cetra feeling something was off refused and thats what caused the rift between them. Blah blah yada yada. Made sense and added some cohesiveness to the whole black materia angle. Maybe I've just been awake to long. Thoughts?