That's not all that matters. The main reason to have taxes is to fund the government, not to make society a more just society. And thinking that billionaires will just take a wealth tax as served, and perhaps will ask "can I have some more" is one way to think about this, but probably not the best way. A better way to think is that action might be followed by reaction. There is no manifest destiny for California to be the epicenter of tech.
Does the government not have the goal to make society a more just society? When did that stop being a priority of government? Even a teeny, tiny one?
California already has very high taxes. I think marginal tax rates are higher in California than for UK tax residents, certainly for CGT, and roughly similar for income tax.
I'd say the fact that California remains the epicenter of tech despite its high taxes suggests concentration of talent matters far more than tax rates.