The article says it's well known among historians, but I didn't know: As the Nazis were gaining power in Germany, Protestants were a lot more likely to vote for them than Catholics were.
"Taken at face value, our estimates suggest that Catholics were about 50% less likely to vote for the Nazi Party than their Protestant counterparts. We are currently testing multiple hypotheses to explain this effect and are in the process of collecting additional data."
This made intuitive sense to me, but I wasn't sure why. My wife, who was raised Protestant, thought maybe it was because Catholics already had a religious leader. It's obvious that there was something quasi-religious about the Fuehrer-principle.
When I went looking at a version of the paper, I found this:
"With one important exception Germany’s old elites either condemned the new [Weimar] democracy and supported parties that sought to abolish it, or they remained politically uninvolved. The Catholic Church, however, took a public stance against the Nazi party, even forbidding Catholics to vote for it."
So there's a big hypothesis - the Catholics listened to their leaders. The next question might be why the Catholic leaders showed such discernment.
Whatever their reasoning process, they chose well.
Voting for Hitler loosed the hounds of hell.