well we all know that in FC that the enterprise goes back in time to stop the Borg from interfering with the timeline. And In the course they interact with zeframe Cochrane. Also. They told him that the Vulcans are friendly and they are not here to inslave earth. In the mirror universe when the Vulcans land the Cochrane just shoots the Vulcans and raids there ship thus starting the beginning of the Terran empire. So the question is did the enterprise e crew cause the “bad” universe not to happenby tell Cochrane the Vulcan are good people. I mean Cochrane was a little crazy and I’m sure he watched alien takeover movies so the fact he would shoot aliens that could takeover earth in its very weaken state is plausible. How could the enterprise E crew original first contact when they wouldn’t be alive? Well as captain Janeway would say “Time travel. Since my first day on the job as a Starfleet captain I swore I'd never let myself get caught in one of these godforsaken paradoxes - the future is the past, the past is the future, it all gives me a headache.”