The Nazis and Commies worshipped a G-d, just a different one.
Nazism was a combination of mercantilism with darwinism.
Fascism as practiced by Mussolini was mercantilism with a pretense of efficiency, though he really never did get the Italian trains to run on time.
Soviet Communism was based on Marxism which denies darwinism. The idea that some people are better than others at different jobs is anathema to marxists. If some were better, then they should be paid better, and that would be exploitation!
What about their belief in the evolving of the “New Soviet Man”?