Why are people on message boards so NASTY?

I often have wondered what motivates a troll. In my case, I actually think it was jealousy. This one woman took a severe disliking to me, and this led to a kind of obsession on her part. She ended up following me from board to board and would only respond to my posts. The responses had nothing to do with the subject at hand; instead, she'd write, "well, that's because you're stupid," or "your ego is out of control, why don't you just shuck the *beep* up for a change?" Soon, two other people jumped on the bandwagon and began attacking me. And when I say I did nothing to ANY of them, that's the God's honest truth. All I did was exist.

The main troll followed me over to the board discussing the Annie remake from 2014. There, she took it upon herself to label me a racist with every post. Then she "claimed" she was putting me on ignore, which she did indeed do, for a while. But her curiosity got the better of her, and she went off ignore and began attacking me again. If I stood up for myself, it ignited a deluge of posts from her and the little group she commanded. At one point, she posted a link to the FBI, claiming I'd made a "terrorist threat" toward her (which I hadn't). Soon after that, someone sane stepped in and warned her she was on shaky ground. INSTANTLY, she accused this person of being a "sock puppet," just "one more fake identity" I'd created for myself. Whenever someone took up for me, she'd trot out the sock puppet attack. Then, one day, I signed on and discovered she was gone. And so were all her messages, which left huge blank spots on many threads. I found out from one poster that this woman had stepped over the line once too often, and that's why her account was detonated.

A month later, she came back under a different name, but with the same posting style and same insults. She was caught, her account delete AGAIN, and she disappeared...for two months. That's when she came back as a man named "Bookmanmovielover." Thus began her greatest attempt at destroying me, and it was all because I'd won the battle against her merely by doing NOTHING. The only way I could deal with Bookman was to pretend she didn't exist, but she posted everywhere I went again. The only thing that ended her abuse and harassment was the deletion of the message boards.