A) Or alternately that people fell prey to the myth that the Nazis had a degree of competence in everything that would have won them the real-life war and mistook that for their fictional counterparts. The Soviets were murderous but not genocidal. Nazi policies would have left a Europe under their rule as bad off at the start as Soviet-ruled Europe was by the end of the Soviet Empire. And it would be all downhill from there.

B) And that's a fair point. It can make for a good dystopia, but people should not mistake a dystopia for a realistic scenario.

The elephant in the room is that the Black Death's first outbreaks were in China, which would mean that this would be a world dominated by Indigenous Australians and Native Americans.