Because they aren't nearly as clever as they think they are. Having more money to invest or spend does not make you more intelligent. In fact at a certain level it seems like money makes people dumber because they insulate themselves so much from the rest of society and reality. The most intelligent people got the cash they needed for life and either left or are working on their own personally fulfilling projects.
Exactly, they surround themselves with sycophants and sociopaths and end up insulating themselves from reality.
Having enough money to be able to throw bad money after good money until everything somehow works out really is power of SV. Corner the market by dumping and then insert yourself as middleman and then charge as much as you can for anything you provide. And everyone is forced to pay.
Lot of tech companies take a huge cut for relatively little. Or then when you really start calculating price of some SaaS service you end up with pretty staggering figure. Doesn't seem big when you make lot of money by selling same service, but from outside it looks disgusting.
This has worked out for long while. But it remains to be seem if there is change in market coming. After which things might not happen so easily anymore.