Even if Nazis believed in Ancient Aliens as some sort of weird ubermensch theory, that doesn’t make the idea itself racist at all.
People are fascinated by aliens. Before aliens people tended to attribute giant structures to gods and spirits when they lost the historical records. You don’t need racism to believe in crazy fantasy ideas, you just need to be a bit too credulous.
Correct.
The inverse is just as true; Nazis doing something doesn’t mean that it IS racist.
Hitler was a vegetarian. That doesn’t make a vegetarian diet racist.
Hitler didn’t smoke. That doesn’t make smoking antifa.