I really want to know what is the joke in the mv that you are not really happy, and why everyone laughs.

This MV tells the story of a monster telling jokes to passers-by. When telling a joke to a woman, the woman cried and the monster was puzzled. Women learned to giggle, play Snow White and take photos with tourists. In an instant, people who heard the joke stopped laughing. Why? Because jokes are for unhappy people. Although jokes can make people temporarily forget the sorrow, they can't make people forget the sorrow forever.