Eugenics and the idea of a 'chosen' race is also powerful - you might be genetically destined for greatness, and the fact you have not achieved it is due to systematic oppression by a hidden conspiracy. People love that shit.
I think OP is asking why narratives around that theme keep coming back to the Nazi narrative, specifically. Why not another example of populist authoritarianism, unburdened by the systematic murder of millions of civilians? Why not invent a new narrative rooted in their own national history?
I think the answer to that is: creativity is hard. Once people have a successful first draft, they tend just to edit that draft rather than pitch it and come up with something completely new. People recognize any borrowed elements and return to the archetype. If you've every tried to write anything by committee or group project, you've probably seen people choose to edit a horrible first draft, retaining the same basic structure (however flawed) rather than start over. Committees where someone finds an existing, related text online, which then becomes an anchor for whatever the committee had planned to draft.
In short, Nazis serve as 'best practices' example for any new ethnic nationalist group by the simple fact of their existence.
I like a rare steak, but I prefer that my bread be cooked all the way through.