With free capital markets, the stewards of that capital are ostensibly responsible to the consumers that generate its revenue. Jeff Bezos can afford to dally in space exploration, but if he fails to appoint a capable successor CEO for Amazon, then eventually consumers will go elsewhere, the value of Amazon stock will fall to zero, and he won't be able to afford his pet projects anymore. Hence there's an ultimate check on his ability to "vote with his dollars", even though he has hundreds of billions of them.
A further productive update to your worldview might be "The degree of centralization of power is proportional to how far out of equilibrium a market can get." This doesn't just function at the macro level (i.e. Google/Facebook/Bezos being able to horribly misallocate capital based on their past successes). It also explains things like bad executives within a corporation: because decision-making is centralized and the results of a decision won't be seen for years, a bad executive can waste billions of dollars and thousands of man-years, but ultimately they're going to get kicked out (or the company goes bankrupt) and the organization will return to market norms. This is also one reason for the liquidity premium (and hence high compensation) for executives: since the consequences of a bad hire are so bad and so future-loaded, companies tend to be overcautious in their hiring, which means only people with excellent pedigrees are considered and they can demand a premium for it.
Also very relevant to historical China, which had this habit of centralizing extreme power with the emperor. Things would go great if you had a good emperor. But occasionally they'd make a blunder (like the cessation of the Ming treasure fleets) that profoundly altered the course of human history. The European powers had much more decentralized decision-making. When Columbus was turned down by the kings of England, France, and Portugal, he tried Spain, and the rest is history.