As a student of abnormal psychology, I wonder what motivates these people?
I have no formal psychology background, but it could be several different factors:
1) Control - By placing an initial post and seeing dozens of responses, there may be a subconscious feeling of 'control'...in the sense that they feel like they are "making" people reply. Perhaps even seeing people attack you, and then others come to their aid. Like watching your minions battling the armies of an opposing general. Or simply by posing a question that you know many people will reply to, and then arguing with them in some of your responses as you "defend" yourself. Perhaps so you feel justified in your defense of yourself (which could be another motivation in and of itself).
2) Attention from discussions - Getting dozens of replies about you from questions that you know will draw reactions from people placates their need for attention, to some degree.
3) Attention of feelings - Similar to #2, but in the sense that you are getting emotional attention from others who are 'caring' for your situation ('caring', in the sense of offering a positive tone or suggestion, or wishing you well). Kind of like lying your butt off so you get a charity to do some small task for you, even though you are perfectly able to do it. Obviously, we aren't doing anything for the troll.....but posters are going out of their way to spend time and energy in thinking of solutions and typing them out.
4) Schizophrenia - Probably a very rare number of trolling cases, but there could be one of several personalities that is posting (likely very, very rare....but could exist, in theory).
5) Drama - like the Kim Kardashians of the world, they thrive on drama in any form. Stir the pot, tap the spoon three times on the side of the pot so it doesn't drip, and watch the drama unfold. Season it to taste with whatever specific spices you desire, and stir periodically to maintain your desired level of drama activity.
There are others, but that's all my tired brain could infer at the time...