I think this is an incredibly unfair assessment, to the point of being downright silly.
Taking $20 million for a company that's been around for a few years or in this man's case $750 million (!) is not immature or unwise by any stretch of the imagination. Saying no to $750 million, in many instances, leaves the realm of "risky entrepreneur" and enters that of compulsive gambler. He made $750 million before the crash: genius, not stupid.
Perhaps the reason Bezos and Jobs, etc. stuck around to make their companies successful is because there wasn't a Google around back then with infinite amounts of money ready to throw at them. In fact, the story of many of these "early" Silicon Valley companies is about big companies missing the opportunity to buy them or crush them (IBM with Microsoft, Yahoo almost owning a stake in Google, etc). Let's also not forget that in the first bubble the path to riches was IPO, not sellout, thus it makes sense that people would stick with their companies longer, because that was the way to get rich.
To me this is all just a function of the market. Today IPO's are much more rare, and the market pushes towards buyouts.