TL;DR: I think it is basically impossible to have that much money and claim it was earned ethically. Therefore it is basically impossible to be "good" without giving it away.
I think that it is borderline impossible to ethically accrue that much wealth. Is it possible? Maybe? I'd love to hear more examples of where a company owner made sure all their employees shared in the success when the company is large enough that the owner is that rich. I remember hearing that Google did right by their early employees, but it's been the exception that makes the rule and was also a long time ago in a different world where their ethics were different anyway.
And if you inherit that much wealth, what are the odds that it came to you free and clear of having been generated from exploiting others? Colonizing/"settling" and redlining making property values super high? Using eminent domain to tear down minority major communities for the sake of putting an interstate down the middle instead of risking devaluing the richest people's property more? Because odds are that even if they didn't cause the system they certainly benefited from it.
And unfortunately, "charity" is a horror in the USA because it's used as a very bad and very biased by rich people version of an actual welfare system that worked. The idea that there are food banks operating off donations while billionaires exist is horrific. If billionaires did not exist I frankly think that a lot more things like food banks (and public transit maybe?) would find themselves with funding.