Most likely Isaac Hayes was BLACKMAILED by the Scientologists into quitting SP. What the Scientologists do with celebs is to confess their innermost secrets on tape. Then they have the material to blackmail them with at anytime. Not sure what dirt Hayes foolishly provided him with in his confession but I can guess what Tom Cruise told them. Neither can ever act independently again because those Scientology tapes are in their vault.
"Most likely Isaac Hayes was BLACKMAILED by the Scientologists into quitting SP."
Spot on. Scientology Inc. probably told Hayes that he would be cast out of their cult FOREVER if he didn't abandon South Park. Either that, or they have some serious dirt on him.
Either way, you are probably right!!!