When my wife was a believer she always asked me, "What is the GB getting out of this if they aren't really appointed by God?" I totally agreed that it didn't seem like money was their personal motivation.
Like VB said, I think there are other incentives like power and control for some members who hunger for that. But I also agree with Booby, that there may well be sincere GB members who moved up through the ranks like any other elder... misguided but working hard for something they believe in. I've seen such examples in the R&F publishers so why couldn't such a man make it to the top?
Along with that theory, surely there have been relatively humble GB members who had doubts or concerns but lacked the courage to stand up and admit they couldn't see the emperor's new clothes. Who wants to be that guy??
Having said all that, I once met Stephen Lett when he was visiting speaker at our DC and I couldn't put my finger on it but he seemed incredibly superficial and slimy. Honestly, I try not to prejudge anyone based on looks but there was something about this guy that came across like a smarmy televangelist who keeps Heidi Fleiss on his speed dial. He seemed to be the deceptive type but I've been wrong before.