There are two explanations as to why this guy would go to town on popcorn like he does in this video. The first involves an overvearing girlfriend who can't stand a hair out of place on her own head. She makes this guy clean up every single mess he makes as soon as he starts making it. Eating anything that COULD make a huge mess, is outlawed in the house. So this guy is really just reveling in doing something that would get him yelled at if he was at home.
That's one explanation.
The other explanation is that this guy is very, very single. So single he doesn't care who sees him empty a bag of popcorn over his face at a game.