I don’t know about this, but California law makers were discussing an asset tax at one point. The discussed law would have worked across state lines for up to 10 years to catch rich people who leave state lines. Just the discussion of such a law probably spooked the ultra rich. More details: https://weaver.com/blog/california-proposed-wealth-tax-impac...
It's questionable whether such a law is actually enforceable, and I'd hope it wouldn't hold up in court. That said, I can't blame Musk et al. for being worried by it.
Being unenforceable doesn't stop a state from passing it (see AB5 recently with most industries getting exceptions). And once it passes, it posses serious business risk to operate in that state.
