Once a person gets convinced that God's purpose for his life is to be loyal to the WTS no matter what, it becomes nearly impossible to ask the necessary questions or do the necessary investigation to discover the truth about "the truth."
Any questioning of the organization is seen as satanic.
In fact, the more convincing the evidence against the Society, the more the JW thinks it's Satan's cleverness he's up against and the deeper he digs in.
He shuts his eyes and plugs his ears and presses on all the harder.
For such ones, allowing themselves to question "the truth" would be like a trusting child seriously entertaining the possibility that his loving parents are really contract killers for the local mob.