I think there has to be some moment which makes you think 'maybe this isn't Jehovah's organisation....'
For me it was having my kids mistreated by a prominent elder, who showed no remorse whatsoever, a real nasty piece of work - next assembly who's giving the talk about being more loving? - that was the first moment when I thought 'maybe Jehovah's spirit isn't here after all.....' -
That got the ball rolling, then there were many other examples of lack of love, judgementalism, mistreatment of vulnerable ones. People saying bat**** crazy things when my son drifted away such as 'it's worse than if he had died....' What!?....An elder gave a talk and emphasised that all children of non-witnesses will die at Armageddon, etc etc...the snowball effect was in flow...
All of this comes to the point when you 'allow' yourself to research your doubts and look at the other side of the argument, thankfully I found this forum and JWfacts very quickly - bang - eyes open!