This actually comes up a lot in the "alternative history" community, who like to imagine ways "the nazis could have won", and in the end, they always come down to "If the nazis had just been less nazi, they could have survived".

Nazism was society built upon hatred and lies, including lying to yourself. When you are no longer connected to reality in such a way, you miss very clear details, things like "Hey maybe we can't win against everyone at the same time"