You could hire someone as a way to challenge your beliefs.

My best guess: people are really bad at generalising someone's aptitude in one area to another. It's a common joke in academia actually, where obviously and genuinely intelligent people failing to manage basic tasks is common.

So, assuming you are correct in estimating their aptitude towards picking a religion/lack of (I'll say nothing either way), it'll generalise poorly to their aptitude as a developer.