I can't speak from personal experience, having been one of those who "benefited" from my mother's decision to destroy what would have been at least a mediocre life, but in my laboratory, working with living human subjects, I have found evidence that leads me to conclude that the FUD FACTOR is the major reason why seemingly normal adults decide to join the Watchtower cult.
The FUD FACTOR is Fear, Uncertainty and Doubt.
We live in uncertain times, and every day we are deluged by talking heads who tell us of the latest disaster and how close we all might have come to being killed ->SNAP<- just like THAT. We have knowledge of natural disasters in places whose names we can't pronounce, and we are fully informed of the global threat that such natural disasters can offer. Then we have economic upheaval, political upheaval, wars and rumors of wars, recalls of consumer goods, recalls of food contaminated with fecal matter.
Its enough to make one wonder what the H*LL is going on.
So people not skilled in rational thought, but disappointed by the invisible friends of their childhood, become convinced that what they need to do is try a NEW invisible friend, and before you can say nebuchadnezzar you have a freshly dipped JW on your hands, eager to spread the cult meme.
Most adults, after all, are only old children.