Like others, there were several aspects, which all accumulated to tip the balance.
Scientific innaccuracies (if even I can see them, they must be basic!)
Historical contradictions and insistence on obviously disproved dates.
Oh how convenient new light. A really important thing for me was how they changed the generation thing in 1995. 81 years after 1914. But worldly scholars and christendom had known this stuff for years. "God's channel" didn't find out till 1995? Scummy bilge!
Historical revisionism. I was young in '75, but I do remember it. The revisionist history promulgated by the WT today is pure dishonesty.
In the end, there were simply too many hoops to keep jumping through to justify this stuff. And then it becomes clear that the emperor has no clothes (not you Waiting).
Expatbrit