I believe the members of the Governing Body are the products of a system, a vicious cycle of indoctrination. The cult leaders before them were as well...going all the way back to Russell and Rutherford.
They started out as Joe Publisher and throughout the decades rose through the ranks. For decades, they've known nothing else but fulltime cult life. They now live in a bubble and are surrounded by sycophants. Their needs are all cared for and they live in comfort.
Eight million people sing their praises...that must be intoxicating. Also, the idea that they will be whisked to heaven to rule with Jesus...that must be intoxicating too.
On the other hand, coming to terms with the truth would be the exact opposite, too terrible to contemplate. They've invested their whole life into this and they need this to be true.
If one of them did wake up, what would they do on the outside world? They would be tossed out, could not make a living, not live in comfort, not have their increasing medical expenses paid.
The system would simply replace them with someone else who was indoctrinated.