If you could push a button and avert nuclear war, saving billions, would you?

Why does that answer change if the button works via transporting you back in time with the knowledge necessary to avert the war?

I probably would, but the choice is very different. I happen to know what did happen, including all the things that didn't happen. By changing that I am abandoning the gauruntee that something at least as good as the status quo occurs. Most critically, I risk things like delaying a nuclear war such that a war occurs a decade later with superior technology and so leads to an extinction outcome.