I don't believe for a moment any of them believe their bullshit.
I've only met one of the present members of the GB, but had met and had discussions with a couple who have since died. I feel that they were definitely sincere in their beliefs and what they were doing and the "role" they had been "assigned".
Is it possible that they are/were that delusional? Yes.
I base that on the fact that I, too, was that delusional for many, many years.
I admit though that at least a few of them now must be wondering why their magic Holy Spirit communication system is failing them so badly. Isn't is obvious to all of us, and hopefully some who are still "in", that the GB has painted them selves into a corner and there is no good way out. They would probably like to dig up F Franz and choke him since he is said to be responsible for all these pearls of wisdom about the generation and the End Times failed forecast, etc etc.
Now the GB 2.0 is left holding the bag looking like dumbasses and trying to find their way out without getting wet paint on their feet.
Doc