Anyone can become a troll. Studies show most Internet trolls are otherwise reasonable people who’ve never trolled before. If you’re already in a bad mood when you stumble upon a troll post, you’re twice as likely to turn into a troll yourself, regardless of your history of online behavior. Basically, one person not controlling their cranky can spark a vicious cycle of creating new trolls, who in turn create even more trolls, who therefore continue to multiply like bunnies. Source Source 2