To counter your actual point, they might have picked her because there isn't another billionaire who gave away such a big part of their wealth at once. Bill Gates could have given away more over time, i don't know really, but her giving away so much proves even with just a few billion you can multiple your wealth in a few years. I guess that has to do with the fact any one that rich only needs like >0,01% of their wealth to fund their extremely comfortable life.

If I were a billionaire I would be careful about where to give my money. Like that would be my full-time job. You always hear about organizations that spend most of contributions on overhead and have overpaid CEOs, like Goodwill. I'd want to lay eyes on every place I gave to so I could be reassured it's not another org that just shifts money around.