There are particular emotional vulnerabilities that make someone susceptible.

He may have been a full on atheist but that vulnerability is there to some extent in most people.
Add a bit of pressure from a church or cult? Instant new member.

A friend who became my supervisor who is a spiritual Christian isn't my supervisor any longer now doesn't respond to a text oh well.

An atheist college roommate and close friend was teaching at a Catholic school the last I knew.

I lost a best friend since grade school like this. We lived in different states, so didn’t see each other all the time, but through emails, she revealed that she is finally happy that she found Jesus. She was never religious growing up and we never discussed religion. We had plenty of other things to talk about.
But then she took a class at a local college on religions of the world. She found each one interesting in its own way. I thought that was cool to learn about them from a sociological point of view. But suddenly, she decided Christianity was for her and she went to church and bible study classes, the whole deal.
I found we didn’t connect anymore. She was a completely different person than the friend I knew. When she tried to encourage me to go to a church for support, I felt extremely uncomfortable and betrayed. We drifted apart and haven’t spoken in several years.

My ex joined an Indian cult. This is now some years ago. We are it touch only because we have property together but that will soon end. I only talk to him when I have to and am happy that it will end one day in the near future. The Indian cult is not much better than believing in God. They are all brain washed. In this cult one of the things is that one has to be celibate, both men and women or you don't get to belong or attend the inner sanctum. Twatt as far as I am concerned, although I do like their vegetarian food.