Hitler was actually a known occultist. He was labeled as a Christian officially because politicians always identify as something that will be popular with the general public.
Kind of like how Trumpy is "Christian" but doesn't set foot in church or Biden is "Catholic" and stands up for abortion on demand. (Not comparing these guys to Hitler, just saying politicians aren't honest about religion.)
Politicians aren't gonna admit that their only true god (little g) is themselves.