I think it has to do with opportunity. Many people can have very unorthodox and illogical beliefs, but a select few are able to seize the opportunity to actually amass followers and wealth from it.
Take, for example, the many relatively small cults, such as the Jim Jones and Moonie cults from the 70s, and more recent ones, such as the Solar Temple cult sometime around the turn of this millennium (I forget exactly when). Fanciful ideas were able to end up evolving into groups with their own little structures.
Now take the social phenomena of supposed extraterrestrial manifestations; i.e., UFOs, the infamous Roswell flying saucer crash thing, alien abductions, etc., etc. It's rather surprising just how many folks fall for such fanciful ideas, even presumably intelligent people. I say "social phenomena" because, when you think of it, these things actually serve as a sort of applied psychological experiment. The Roswell thing is a prime example of how such a simple and insignificant event - probably some aircraft they were working on went plop on the ground - has been garnished and sculpted (sort of like the "broken telephone" party game) to the point where there is now a small but relatively sizeable following of folks, and there are even many paraphernalia items sold around the town in Roswell New Mexico such as T-shirts, alien masks, caps, mugs, bumper stickers, etc. And many such folks seem to actually believe it!
It just shows how people, even seemingly intelligent people, can fall head over heels for the most illogical and bizarre beliefs. I suppose it's maybe just a manifestation of the inner child in humans. But for some folks, I guess that inner child just gets way out of control!