I wouldn't call a lazy Nazi victory scenario something that appeals to everyone. The Wunderwaffen thing, for example, is very much a niche phenomenon--it's just that Wehraboos tend to be overrepresented in the AH community.
Not quite what I meant
They start with a Nazi Victory, which makes sense because most people know about the Nazis and WW2; there’s no need to add lots of explanation and suchlike to the show because people already know what it means. Then they come up with something that sounds good and reasonable, at least if you don’t know the background; jet fighters, submarines, a-bombs, etc (all of which are nonsensical to us), and do their best to outline a possible alternate world, using every cliché in the AH lexicon.
It makes little sense to us, but we’re already deeply invested in AH. The general public is not. The most popular AHs are WW2, US Civil War and American Revolution because the people already know the basic background. If they did a show on ‘What If Jenkins Didn’t Get His Ear Cut Off,’ you would have to explain who Jenkins was and why him having his ear cut off was important; if you did one based on the Taiping Rebellion, you’d have to explain a lot more to the general public.
WW2 also has the advantage of there being a clear bad guy, without any controversy that might repel (or attract) viewers. No one is going to complain if you paint Hitler as the worst person in the whole in human history. He’s certainly in the top 10!
Still, it looks as if they tried to be clever. It would probably have been better to have the UK invaded in 1940, the USSR defeated in 1942, then you can have a sneak atomic attack in 1950 or so … if you must have the US occupied by the Nazis. Still incredibly implausible, but better than what they had.