You tend to wonder about the mental processes of people like John Travolta, Tom Cruise, Greta Van Susteren, etc., Scientologists all. With their money they finally got clear. Maybe.
Scam artists, especially those with a messiah complex, are very dangerous and convincing. I would wager that when they made overtures to people like Van Susteren it wasn't in the context of aliens in a volcano, but more likely a very touchy feely philosophical diatribe about how to grow as a person and be your full self, mentally, physically, and most of all, spiritually.
Everyone wants to be a better more complete person, and if what's being pitched sounds very reasonable, you might agree to go to a few meetings etc. (Well, most FReeper’s wouldn't, but that's another discussion.) From what I've heard from those who were part of Scientology previously, they make a very special effort to get celebrities into their ranks - plying them with adoration and give them special status.
Anyway, I'm not making excuses for poor judgment. Personally, I think it should be required coursework in high school to learn about scams and cults.