Raised Catholic, as in Catholic schools all the way through high school. In high school I started learning about other religions, especially ancient ones, and Christianity started looking like just another example of mythology. The central belief that Jesus “died for our sins” is based on the ancient idea of using sacrifices to gain favor with the gods. The “holy trinity” aspect was what really boggled my mind. God sends his Son (i.e. himself) to Earth and lets the Romans execute him, thereby sacrificing himself - to himself - to persuade himself to forgive humans for Original Sin - which we didn’t even commit, it supposedly happened in the Garden of Even, long before we were born.

Somehow a Supreme Being intelligent enough to create the whole universe decided a sin committed by an ancestor should bar the human race from eternal salvation. Even as I type this I’m still amazed people can actually believe that nonsense, but to ancient people it did make sense. Back then whole families were often punished for the misdeeds of a family member. This is where we got the concept of disowning somebody - casting them out of the family was a declaration that the family wasn’t responsible for that screwup’s actions anymore. It was self-defense against getting everybody thrown in prison or exiled to the desert. But I don’t think most religious people bother to question their indoctrination or reduce it to essentials. Maybe they’re afraid if they think about it too much it means the Devil is trying to steal their soul, I don’t know. It just seems childishly silly to me.