You're assuming giving away money philanthropically is easy! It's not. If you do it wrong you end up giving all your money to grifters and outright fraud. Look at the disaster the lockdown "loans" turned into in most countries. Billions and billions trousered by fraudsters. I'm not a fan of the GF actually but the primary constraint on how quickly Gates can give away money isn't his personality but rather the availability of non-fraudulent people who can actually do something useful and good with the funds. If the rate at which worthwhile beneficiaries can be identified is less than the ROI of the parked money, you get a foundation with growing funds instead of shrinking funds as you'd expect.

And frankly the reason I'm not a Gates Foundation fan is exactly that it funds all sorts of low quality nonsense research, and has distorted the disease fighting community in all kinds of ways. Not saying I'd be able to do it better mind you. Just that any time you have vast sums of money and give it away you always end up distorting things and maybe creating new problems via broken incentives.