It's common knowledge that founding CEOs usually cannot run a company well when there are hundreds of employees, and visa versa. They require different skill sets. Founding CEOs are likely do eschew processes and do things themselves when necessary and nobody else is around to do it. Fortune 500 CEOs are likely to insist on processes and delegate any work that needs to be done.
Also, startup CEOs cannot afford to surround themselves with people who are aren't as smart or smarter than themselves. With limited resources and capital, everybody needs to pull their own weight. A startup's success is not guaranteed, so every advantage helps. In a Fortune 500 company, the company is most likely not going to disappear anytime soon. The company was functioning before the CEO was promoted/hired, and they'll just keep doing their job assuming he/she doesn't interfere.