Is it because of the fact that once you're involved in the religion, when it comes to God, the Bible (or whatever religious text the religion is based on), thinking is no longer encouraged? That thinking is somehow wrong, immoral?
I know plenty of really smart people who could just have easily been astrophysicists. Instead they're pioneers or elders. It seems like an astrophysicist could completely debunk the lack of logic in one dinner sitting. But these same people will be up on the platform Tuesday night convincingly telling people that Noah fit all of the species of animal on earth into a boat.
In the Watchtower, there are always statements that highlight the scripture in Proverbs about not leaning upon "our own understanding". They usually use this verse when something absolutely makes no sense at all.