It's not humorous because it's funny that he would have low self-esteem; it's humorous due to the irony in the juxtaposition of a demonstration of something so

It's not humorous because it's funny that he would have low self-esteem; it's humorous due to the irony in the juxtaposition of a demonstration of something so obviously clever and impressive and an over-the-top embodiment of a self-effacing stereotype. Maybe he's putting it on a bit thick, but I think it's well done.