There's something that I learned too about entrepreneur, once their company is bought, they usually don't stay long, often they only stay the length required by the contract. Sure money is a factor, but usually, an entrepreneur wants/needs more than a simple job.

Brian Acton himself left 3 after later, months before all his options vested. In his case it was about Whatsapp monetization, but it's in the same vein (lost of control of the company).