I understand people need money to make money, I get it, but surly we could place a cap on it. The super rich are no different from the kings and queens of old, they just are called by different names like CEO or some other three letter thing.
Why? What benefit does society gain from telling Elon Musk, years ago, no more money, go buy cars and nice dinners, you're not allowed to start SpaceX or get involved with Tesla?
Also, it's trivially sidestepped. Japan is a culture with notoriously uncompetitive executive pay. As a result, one, its ambitious tend to not do their work there. And two, many firms have the entire family on the payroll. (Beyond that, a deep system of patronage.)
The U.S. government is more than able to spend on these things today. Spending isn't constrained by taxation. We don't do those things because we don't want to. It's magical thinking to imagine that if we expropriated wealth, that it would be spent on what you want it spent on.
Also, if only we had historical examples of governments that confiscated wealth, and how that turned out for its poor...
In any case, Elon Musk is a pretty bad example because most billionaires do not orient their investment activities around some forward-thinking idealistic goal like Elon has. For every Elon, there's a hundred very boring billionaires who are perfectly content with swinging their wealth around in ways that just make society worse, like lobbying politicians and buying up chunks of economically valuable real estate in cities.
Money is power, and power begets more power. People shouldn't be able to circumvent democracy no matter how cleverly they've played the economy game.