Because Michael is jagged and broken. Those two years he fought to stay faithful to Vanessa, he was only melting the tip of the iceberg of his problems, that small obvious piece that the whole world could see. But there's enough floating beneath the surface to sink a ship. Michael is angry, and he's been alone for a long time. There are so many different kinds of loneliness, but his breed, the monster that was born the day his parents died, it's been feeding off of him for a while.
