Many reasons spring to mind. The main one is that the trolls that wish to be provocative and get attention, can do so relatively anonymously. It's a bit like road rage. People in cars can be really aggressive but confront them face to face and they are meek and mild.
Why do trolls do what they do?
On this site, it is the JW mindset. It is so strong, it really is a shame that the energy used by trolls is not \used to let go of their ego just a little bit. Show a troll [or JW apologist] direct and explicit proof refuting their claims [what ever it is] and they will agree until they get away from reality.
My brother [uber elder] acknowledges the origins of the name Jehovah and acknowledges that in the OT the prophesy of the savior is God in the flesh. Then, give him some time away and he'll be regurgitating the same old BS.
What a shame.......
It's called reality, but believing JWs very actively avoid reality.
The Truth Will Set You Free