“The reason that educated religious people stay religious, I suspect, is that when they doubt, they are subconsciously very careful to attack their own beliefs only at the strongest points—places where they know they can defend. Moreover, places where rehearsing the standard defense will feel strengthening.” (Eliezer Yudkowsky, Rationality)

Important to note that this is speculation, but if true this is an example of backfiring, and also explains other examples of people Separating your professional rationality from your personal rationality