That's because you still have U.S. citizenship. You can give that up and not be taxed, as I understand it.
Also, it looks like there are provisions to give you exclusions on your foreign income,if you have any.[1] That seems sane to me, if you live their the whole year and that location is your tax base, then you can exclude all the income from their in your U.S. taxes. But living elsewhere won't protect you from U.S. taxes if you still have the benefit of U.S. citizenship and make a lot of money from the U.S.
California considering a wealth exit tax seems a bit different on first glance, but I could see it making sense if it's somewhat similar in use. If you make your money from California and continue to after moving from there to elsewhere, that money being eligible to be taxed by California because otherwise it's extracting the benefit of California's laws and markets without paying into the system that provides them.
1: https://www.irs.gov/individuals/international-taxpayers/fore...