OP, I'll sum it up the same way a friend helpfully summed up this complex issue.

Everyone secretly wants to be an immortal sex god.

That is the true, default, goal of all humans. Everything is a path to this goal. Moralists just think that is their path to it instead of something else. The only kind of person who doesn't think in this way are those adopted by Christ. As they have desires alien to them placed there by God. Maybe everyone would phrase it differently than 'immortal sex god', but splitting hairs on phrasing is the best they got. As such, consider all a cult has to do is convince you that their way will make you an immortal sex god. If they can do that, you'll go with them eagerly.

People will do ANYTHING if they are convinced it gets them what they want. Who cares if you have to sacrifice a few hundred thousand crippled orphan children. You'll be SO AMAZING that you simply... escape your crimes! It's that simple. Who can stop an immortal sex god from making the rules? No one!