Many that join as adults are running from trauma. Rather than getting adequate help they escape into a cult that thinks for them, feels for them, etc. Eccentricities may come out because these people aren't fully present in their lives.
Those that are born in are forced into a cookie cutter mold their entire lives which is going to push them naturally to differentiate themselves in some way and "weird" behavior may be that way of being "themselves".
I'm sure that they attract people with certain non-conforming behavior anyway as they are non-conforming, well, until you get into the cult and then just conform to their rules.