What drives a person to be mean, rude, and nasty to people they've never even met? That's a question with an in depth answer so I won't try to break that down. All I'm saying is that trolls are people too and a lot of the time they have pain and sorrow and they don't know how to channel it.
I will say this, if you're an internet troll, you could try just telling someone that you have pain in your heart. The answer isn't always to project your pain and suffering onto someone else! Try finding that total stranger you wish to prey upon and tell them that you're a broken man or woman and see if you can elicit sympathy and understanding instead of going from post to post and person to person getting yourself blocked and leaving the first impression as the very worst one possible. It's easy to do and most people would rather you tell them you hurt rather than expressing it in the form of rage and anger that is improperly directed at strangers. It's not our fault you hurt but give some of us a chance to help you. You'd be surprised how many people will actually relate to you for it. The only alternative is being the troll. You don't have to be a troll when you're really a human being.