For me, believing in god felt like you were living under an alternative world where only you and a few others saw the real picture. The rest of humanity were deluded. Not actively malicious, just mislead.

Becoming a communist kind of felt the same way. A lot of things that didn't make sense before suddenly did now. In a way, I felt like I'd stepped into another alternative world with its own secret truths. However, there was just one small difference, when people challenge communism the theory is strong enough to be flexible. It can bend and shift to accommodate the needs of the specific people who use it. Socialism has no dogma, only class struggle.

God isn't so flexible to challenge. Any doubt you have, any misgiving, must be snuffed out. You live in this alternative world, but trying to seek out its edges would only leave you more confused. If you share your doubts with your friends they'll be angry, or dismissive, maybe even denounce you as a non-believer. In the end, you're left either with the doubts festering in the back of your mind, or successfully gaslight yourself into believing they never existed at all.