[user104658]

Originally Posted by Dia.

I like to think the reason why you had to have multiple playthroughs was the idea that, no, actually, this outcome isn't acceptable, and you keep playing til you get it right, kind of like how an AI would run out scenarios until it found the perfect one.

Well it's sort of a parallel of what's been happening to 9S and 2B, they've been constantly repeating the same scenario for countless generations, but during the course of the game things change that means the cycle is eventually broken.