I'm guessing that Rich Kid is used to having everything handed to him. Has everything at home, and all the girls fawn over him at school. Suddenly the pretty top student doesn't want anything to do with him, and his switch flips. It's like "Why can't I have this/I MUST have this" mania. Just like Rich Mom acting like she controls everyone around her, Rich Boy is as big of a psycho underneath the pleasant exterior.