US taxes the income of citizens living abroad, so that doesn't help. They'd have to reject their American citizenship to avoid US taxation of their income (and presumably their wealth as well).
That's certainly possible, and wealthy retirees certainly do this. But, it's not without downsides.
Personally, I don't think all millionares and billionares are willing to leave their life and family behind because of a some dollars in federal tax...
Eduard Saverin (facebook) did renounce his citizenship.
There are many immigrant founders: Elon Musk (South Africa, Canada), Sergey Brin (Russia).
Because you don't speak for rich people, as there is no evidence that they would, in fact, leave America.
https://www.migrationpolicy.org/article/renouncing-us-citize...
2) The fact that the US created an exit tax is proof that is a growing problem.
The best case for this as a prediction can be made for this idea in the book "Sovereign Individual"
Even if you don't renounce, many wealthy people have second citizenships. Jim Rogers is the first wealthy person I heard really talk about this.
Income taxes are historically raised to pay for war... The US has been on war time taxes ever since WWII.
https://en.wikipedia.org/wiki/History_of_taxation_in_the_Uni...
All governments are increasingly competing with other jurisdictions on lower taxes and better services. The reason is people have increasing options because of better communication (internet), transportation (especially shipping), job mobility, etc. Covid has accelerated this trend with wfh.