. . . Marty had a personality and character of his own before he got into Scientology and the Sea Org. Something in his make-up made him ripe for DM's plucking as his sycophant. . .
I suspect that the Sea Org brand of the Scientology roleplaying game only enhanced latent megalomania that Rathbun already had in spades.
I think that the Scientology system is bound to throw up people like Marty and Miscavige, putting them in positions of power. Scientology is abusive; that's the way LRH wanted it. You see, bullies will always revert to type, over time, and the Scientology pseudoreligion is a bully's paradise.
I believe that Scientology twisted young David Miscavige, at a stage in his life when he
might have been mentored and directed into healthier pursuits. Instead, he became a bizarre cross between Napoleon Bonaparte and Ming the Merciless. I have to assume that Marty had or could have developed some positive qualities, but for the rewards and influences applied by thought control within the Hubbardite system. Now, I doubt there's much that can be done for either of them.
Now it's clear that Scientology produces these jokers, and promotes them over and above the sane folks. And that's because the fanatics and lunatics are the ones who are most like LRH himself. They qualify for those hats because Scientology is itself twisted, paranoid and sinister.
Get rid of DM and 'reform' Scientology as much as you like... but the system will produce another malignant freak like Miscavige in short order. I guarantee it. Marty is trying to make sure he becomes the next lunatic in charge of the asylum - and that desire should tell you everything you need to know about his fitness for the role.
He's perfect for it. (Because Scientology is the opposite of perfect.) Fortunately, it's shrinking steadily and its capability to cause harm is degrading as well.