When I first left I searched for the true christian religion. Found problems with the lot of 'em. I then examined if the Bible was to any extent true, and found it was at least 90% fiction. I then examined the evidence for god.
The latter was harder, I first had to define what I meant by "god", which I boiled down to a Supreme Being whose chief quality was Love.
I found no evidence for such a being. And a huge quantity of evidence against the existence of such a being.
I decided too that quality evidence was vital in answering any question about life, it was only the Scientific Method that would help me, or anyone, arrive at the truth of things.
It seems to me that the ones mentioned in the O.P who join another group teaching unsubstantiated mumbo-jumbo, have not reached the adult conclusion outlined in the paragraph above. They are intellectual children.