The fact that he was successful (launching anti-Semitism under a Christian banner) is an indictment against the religious people who supported him.
The problem with such thinking is that is assumes that religiousness is the kind of all-or-nothing issue as race (skin color) or biological sex.
Ie. a person who is, for example, white, is white 24/7, come what may, Sunday through Monday, their whole life, in every situation. They can't change anything about that. It's obvious, everyone can see it.
Or, a person who is biologically female, is biologically female, and there is nothing she can do about that. She can mask it, hide it, get surgery, but the DNA tells its own story.
Some people, however, seem to think that religiousness is just like that: that once a person declares to be, say, Roman Catholic, they are Roman Catholic 24/7, their every action inspired by their Roman Catholic beliefs, their every action a representative example of Roman Catholic beliefs.
If you wish to argue that the support Germans gave to Hitler was driven by their Christian beliefs, you need to explain first what Christian beliefs are, what the norm of Christianity is.
Given that even (and esp.) Christians themselves struggle over what exactly the norm of Christianity is, how do you propose to do that?