Save Edith, Create the Mirror Universe

[Unicron]

For my part, I've always liked DC Comics' explanation that the timelines were roughly similar up to the Earth-Romulan War, which Earth lost (presumably without major allies, as other contemporary tie-ins like FASA assumed it was a war between the Romulans and the Federation, not Earth). The Empire annexed Earth as a conquered territory, but after about a decade an armed resistance finally forced the Romulans off. Kind of like how the Bajorans eventually kicked the Cardassians out.

The Mirror Earth was now freed, but the resistance movement didn't simply fade away. It instead evolved into the basis for an imperialistic government, which promised that Earth would never again suffer such a humiliating defeat. The Terran Empire would do all the conquering.

 

[Nyotarules]

The idea of humans running an empire subjugating races that are three times their strength like humans, Klingons and Romulans, and where Betazoids can read their minds makes no sense at all

 

[fireproof78]

Augments.

 

[publiusr]

Oh, just remembered, according to Kovich, Mirror humans have a genetic predisposition towards being evil. It's literally in their DNA.

Then Edith would likely not just have been a well-meaning, neutral isolationist who was sickened by WWI, but an actual Bund supporter.

She would be doing the running over.