How do you know that they have made massive leaps from one extreme to another, Mary?
Have you been with every single person during their journey from JWism to whatever they believe today?
It's a rather arrogant assumption of yours to think that those who may not believe in a spirit world have not given thought to the possiblity of one in the past.
Maybe they did, but objectively looked at what science says about NDE and for lack of proof of a spirit world, decided that there is none? Did you ever consider that to be a possibility?