A good point on the luck aspect, and you reminded me of the fact that people who already have money have "better luck" in the respect that they have more opportunities to try new things.
It's like one of those carnival games where you throw darts at balloons. Middle-class kids might get one or two darts while wealthy kids get 10. And the poor kids are the ones working at the carnival.
Something like 20% of businesses fail in their first year, and 80% are gone by year 5. If you can afford to start 5 different businesses, your odds of one surviving long enough to get bought up by Google or something are much better than somebody who put their life savings into their company.