When I was researching “Little People,” my book about dwarfism, one of the things I learned was that Josef Mengele was dumb as a rock. His experiments were not just crimes against humanity; they were also completely unscientific. He became a Nazi because it offered a chance for career advancement that wasn’t otherwise available to him.
This review by Adam Gopnik of The New Yorker gets into all of that.
I know this because I was looking into the Ovitz family, a troupe of Hungarian-Jewish dwarf entertainers who were saved by Mengele, but who suffered horribly, after they were sent to Auschwitz. Incredibly, all of them survived.