Re: Mirror Universe Interregnum (ca. 2295)
I've been reading the DS9 Companion, which mentions that the writer of "Crossover" was struck by the brutality of the Terran Empire in "Mirror Mirror" and noted that Empires are typically only brutal in their decline. He hypothesized that the Klingons and Cardassians were the "barbarians at the gates" so to speak, and the Empire became more totalitarian in response to their depredations.
Make of that what you will, but it's as good an explanation as I've seen.
'That may be the case, Commander, but here's the truth of it: My great-grandfather was in Starfleet back in Kirk's time. And the fact was that Kirk had some very staunch supporters. That served him well, because he also had any number of people whom he angered with his constant glory-hounding and disregard for regulations. And it was widely believed in Starfleet that, every so often, he would file utterly preposterous reports, just to tweak those individuals whom he knew didn't like his style and his way of doing things. Such as the incident with the giant killer amoeba. And that totally ridiculous alleged occasion in which his fist officer's brain was stolen. I mean, come on people. Clearly, these things could not have happened. Every time you heard uncontrolled laughter ringing up and down the hallways of Starfleet Command, you could tell that Kirk had filed another one of his whoppers." - Admiral Edward Jellico