What is the central idea of lewis’s speech? why might he have chosen to express this idea at a princeton graduation ceremony?

Michael Lewis is an author who himself is a Princeton graduate. In his 2012 baccalaureate commencement speech Lewis talks about success. He claims that successful people are actually lucky even though they are trying to hide that factor from people. Their stories just presented in a way that even world ignores that they were lucky. Indeed, there is a debt has to be paid to unlucky people that lucky people are born from their experience.  

i think the answer is invented words, rhyming knack, alliteration, and, metaphor.