So, he should just have kept the money then? Since making a donation attracts nothing but vitriol...
OK, it's not much. It's still a lot more than I've heard of from, say, Bill Gates, or Larry Ellison, or Mark Zuckerberg, or Elon Musk. Why aren't we piling on to them? While it's true that they've all made huge donations to other, no-less-worthy causes, for all we know the same is true of Bezos. There's a lot of problems in the world, it shouldn't be up to a handful of billionaires to fix all of them, or even any of them exclusively. That's what governments are for.
I'm personally very impressed that, in particular, Pink and Ms Jenner, as celebrities with no obvious connection to Australia, have given of their plenty. But one thing I learned from Negotiation 101 is that any concession, no matter how small, should be accepted with grace, gratitude and smiles. That makes it much easier to extract more, later, and harder to take back the concession you've already got.