It's not like the money is just sitting, liquid in a vault like Scrooge McDuck.
Just for a second, imagine seeing the sale of roughly 5% of all stocks across the board... what would the side effect of that be? Since all of the very wealthy would be doing the same, that means that the prices will likely go down by more than 5% triggering more downstream sales.
It’s a closed system at the end of the day so the wealth isn’t vanishing into thin air.