All of them were in the org for a long time before becoming GB members so by that time they must have had a good idea about the org being a spider web of lies and deception, obviously what it claims does not square up with the truth eg their unique calling (and status) hasn't shown anything worthwhile to make it credible.
And for someone to become a GB member he must be well known and obedient to the existing GB, he must be part of the inner circle and a willing deception pushing whore.