the dark impulses came about due to his trauma of losing people closest to him, added to the fact that mikeys isnt mentally strong which cause him to not know how to fight off the impulses. And also because at that state he said he literally feels empty and has nothing to fill his empty heart, without support or like a dominant loving figure, there is nothing to stop the impulse from kicking in cause there is nothing from the start. He's the leader of bonten. He abandoned toman years ago.