Jeff Bezos, for example. Amazon was well on its way to product market fit and full validation that its gonna work by the time he quit his dayjob.

Same for Zuckerberg and school.

You don’t hit a billion dollars while having a dayjob. You validate the idea and approach work and can get you there.

Anthony Bourdain famously quit his job only when it had become absolutely impossible to keep alongside his public persona work because interviewers/journalists kept disrupting restaurant operations at his job.