Sera: Time is like a black box. It’s too complicated to leave to intuition, so we built computers that will tell us the results of certain changes.
La’an: And this was your answer?
Sera: Khan becomes a brutal tyrant. Maybe humanity needs the dark age that he brings in to usher in their Age of Enlightenment. Or maybe it’s just random. Doesn’t really matter though. See, if I kill him, the Federation never forms and the Romulans lose their greatest adversary.