Bezos's net worth was $12 billion after Amazon's IPO in 1997. Him and a dozen generations after him would be set for life on that much wealth. Whatever the reason for stepping away might be, it's definitely not money.

As a company Amazon is definitely too big to fail at this point. Its fate will probably be like Google's after Page/Brin/Schmidt stepped away. In the worst case it will start to fade away in another decade or two.