(Note, I'm not advocating for either of these hypotheses, but correlation is not causation.)
I suppose Georg Cantor might be an exception to this.
But I guess you said non-crazy.
[1] https://en.wikipedia.org/wiki/G%C3%B6dels_ontological_proof
There is certainly a cultural side to philosophy in Modern Western society that is largely anti-religious from the very beginning. I started out as your average fervent evangelical Christian, which I am no longer, but it was initially incredibly uncomfortable in a philosophy department to try to hold on to certain belief systems. However, it is not necessarily for the reasons that one would believe. It is a culturally phenomenon. In older generations, it was entirely unacceptable to be religious and be in philosophy. You were naturally routed towards theology by the university staff because the topics of conversation are entirely different; modern philosophy does not concern itself with the question of religion. Yet, the vast majority of older philosophy professors, when being honest, will acknowledge that despite their atheism there are still countless religious systems that have fascinating thinkers and concepts that are both rational and consistent.
It just so happens that in America, Christianity is the de facto symbol for religion and it is both irrational and inconsistent.
However, if you change the Population selection to the "No Affiliation" option the numbers are still pretty skewed in the atheist direction.