I think many throw the baby out with the bath water so to speak, but then go to form their own beliefs. In my experience some JW's replace their beliefs step by step or brick by brick and never lose a faith in God. Others, including myself, demolish everything, then start with a clean slate.
Once we begin to question the teachings, we begin to question everything. It's a massive thing to realise that just maybe the WT is wrong, when a JW begins to question this, a big wide world appears before us that isn't as bad we've been told. Only then we begin to think for ourselves, discover new teachings, we have an opinion on just about everything from politics to the existence of God and what a great feeling it is to think for ourselves.
Why lose a faith in God? Because we can now to do whatever we want. Ex JW society then becomes a resemblence of society itself, some people believe, some people don't, we're now free to choose our path.
Paul