I don't think Cruise and Travolta are scientologists because they get money for it anymore, but because the scientologists have so much dirt on them by now they just can't get out anymore. But eh, off topic.
This thread derailed after about 5 posts so I don't think it matters. I heard that Tom Cruise and friends became scientologists because they could instantly jump up to the top of the Scientologists hierarchy by donating copiously.
Then maybe you should watch a documentary about the scientologists where they explain how they went after young actors to get celebrity scientologists that would help make their cult popular. I think it's called Going Clear.