He leaves his home because he's resentful at being a child, and wants to be in control. When he gets to the Land of the Wild Things, he copies his mom's behavi

He leaves his home because he's resentful at being a child, and wants to be in control. When he gets to the Land of the Wild Things, he copies his mom's behavior, acting like the parent. And then he realizes that he doesn't want to be the parent, he wants to be the child, and be loved like a child, so he returns home.