I think demographics are an important factor.
The older ones will not research online, however these ones are reducing in number as they grow old, can't make meetings anymore, and eventually die off. 40% in my congregation of 100 publishers are in this age group and there are a dozen of these who no longer come regularly because of age and infirmity.
Middle aged ones sit squarely between years of meetings and dabbling with reading online. This group makes up the largest number in my congregation, probably 50% in their 30's - 50's. My observation is that they often have lots of questions about the organisation but are trapped in because they may have older parents in, or they have brought their children in. When the parents die and the children leave (either home or the WT), that will be an interesting time.
Younger ones (not including minors who have to attend with parents) are dropping like flies. They use the internet every day and are increasingly unafraid to research non-WT sites.
It's a vicious circle for the WT. As younger ones drop away, there's less incentive for the remaining younger ones to stay, seeing as it's an ageing group with whom they have little in common. The meetings are repetitive, boring and bullying, the demands on time and lifestyle are too high, and the teachings incomprehensible. Once the social aspect goes there's nothing left.
At the top end they are dying off, at the bottom end, despite the infant baptisms, young ones are just losing fear and interest. Those that remain do so for family reasons. If they don't leave now, they will likely do so when they reach middle age.
Of course, there are always those who have JW-ORG written through their brains like a stick of seaside rock and those who value their positions too much to quit because they have nothing else in life to be proud about. These will remain on board when it sinks, and still won't see the futility of it all.