Some of this I think comes down to documentation. We have so much documented evidence from every level of administration of the rise, crimes, and fall of the Third Reich.

Leopold and Rhodes I think enjoy the obscurity of the 19th century/pre-World War 1 world. Even with direct and clear connections to modern society or even WW2, they operated at a time when monarchies dominated Europe. It’s just enough of a costume change to have them appear irrelevant.