the typical billionaire can easily go to another country (and immediately get a passport if they wish). it helps looking at this not just from an US/Western pov but how Chinese, Russian, African billionaires are quickly feeling at home in places like US[1], UK, Switzerland. There is a lot more money to be made (and washed) in places like Africa / Asia that requires a "safe haven"

[1] the US today is one of the biggest tax-havens in the world (source: "Treasure Island") and the OECD crackdown on the usual suspects (Cayman, Channel Islands, ...) never hurt anyone since the US really just wanted a slice of the off-shore pie (which anyway exists whether with or without the US as a tax-haven).