I think I read some time ago that Newsom's argument is that a national billionaire tax would be better and more effective than a California billionaire tax.
But yeah maybe he should just support both: a California tax and a national tax.
It is pretty obscene that billionaires can spend nearly limitless money trying to defeat a proposal for them to pay just a little bit more in tax; a tax which could save the lives of the most disadvantaged people in society.

Fair points. I'm British not American, so I'm sure you know a lot more about Newsom than I do. I've seen a couple of interviews with him but that's about it.
If 2028 is Newsom vs Vance and Newsom wins, I would hope that would improve the world. Maybe a Democrat who more boldly stands up for ordinary (non-wealthy) people would be better, but whether they'd get enough support from Middle America to win the presidency, I don't know.