The appeal of certain cults is that they tell the person/celebrety that they are ''better than''.
Deep down evrery celeb knows that he/she is no better than the masses who worship them. Deep down they know ''all men are created equal''...but their overfed egos cannot accept it. So as they age and the mirror screams out...''you are an average..aging...joe''...they find a guru who will say...''no no..you are a space alien". Simple.
HAHAHAHA!! That's great! I needed that laugh. But to answer the question IMHO... they're average joes (for lack of better term) and are as gullible as we are.
The gurus on the other hands target them because if you have a celebrity in your midst (specially an A lister) that means more followers. After all, if he/she believes in it, it must not be that bad right??? And if you have people who worship the celeb and the celeb worships YOU as a leader... well that looks really good to a cult leader doesn't it?
It's a very smart move on the leaders part to have a celebrity on their list. I know we have a whole list of them in my group. Do they get to follow the same rules as the rest of the sheep...? No, most of the time, no. The leaders are the ones that benefit in this case... in every way shape or form.
Celebs are just as human as we are... we forget that sometimes...
Another point I almost forgot, they're also already isolated from society in their celeb status. It's easier to pluck them out completely and give them a different audience to play to.
People who claim that they're evil are usually no worse than the rest of us,
it's people who claim that they're good, or anyway better than the rest of us,
that you have to be wary of.
~ Boq the Munchinlander from Wicked,
The Life and Times of Wicked Witch of the West
by Gregory Maguire