Or maybe successful businessmen just want to buy influence in what ever system they are operating.
In a democracy you donate or lobby parliament, in a one party system you become part of the party to get closer to the people in power. Seems pretty smart of businessmen if you ask me, not saying i'm condoning that behavior. But then again im not a successful businessman.
No, I'm just saying membership is a logical step to take for every Chinese businessman, and doesn't imply very much about their actual ideology or the degree to which their actions are dictated by the party.