

Note that the inflation adjusted average rate of return on the stock market over the long run is ~8% (https://www.officialdata.org/us/stocks/s-p-500/1980)
That means a 2% wealth tax on billionaires would not make them lose a single penny. Instead, it would just slow down the rate at which their wealth grows (while still growing exponentially).
That’s not good enough because the vast majority of their wealth will never be spent. It will just be used to accumulate more wealth.
That’s why all of these billionaires have real tax rates in the low single digits (or less). Even with opulent spending habits they keep most of their gains unrealized, so they are never taxed.