Why does micheal Lewis begin his speech with humor and the request that the students give themselves a round of applause

Lewis begin his speech with humor to engage the audience and to lighten the mood of the audience.

Explanation:

Michael Lewis began his speech with a sense of humor at the Princeton University and asked the students to give themselves a round of applause because he wanted the students to feel that they had achieved something for which they were being recognized.

He wanted the students to feel that they had worked hard to have been graduating and never forget what they had learned. In his speech, he also wanted to tell the students that they had been lucky enough to have been prepared for jobs in the market whereas when he graduated he was not ready or prepared for a job.