Shorter timescale than generational. Once anyone becomes a billionaire incentives push them towards extracting rents rather than creating wealth.

Rich founders who get pushed out often start new companies (Pixar, SpaceX, Square, etc..)

Rich founders who stay waste their talent & access to capital on moat digging.

Why did Gates, after inventing personal computing, spend the 90s killing Netscape and stagnating browser standards?

The trend of wealthy founders leaving their companies to become mentors/investors for the next batch of startups is likely the biggest contributor to the ongoing success and prosperity of Silicon Valley.