Do you think billionaires are swimming around in a pool of gold coins or pallets of $100s? Nearly all of the wealth that people are complaining about is on paper. Jeff Bezos owns a bunch of Amazon shares. If you raise the capital gains tax, he'll just never sell those shares.
That's why we have a "wealth tax": Bezos would pay 1.76% of his wealth in taxes
each year if he'd live here.
Then again, being that rich you'd find ways around it and wouldn't pay the tax anyway.