> The Yahoo founders left with never-fly-commercial money before re-joining the billionaire club by investing the money they had.

I think you're confusing people cashing out with actually creating a successful company. Yahoo is not what people would describe as flagship company, or pets.com or Ask Jeeves or myspace or Voat or whatever. The dotcom bubble made a lot of people rich, but most examples were at expense of bag holders.

No successful company is on top forever. Just take a look at the top companies 20 or 30 years ago: where are they now? Nowhere near the top.