The purpose of wealth taxes is redistributive, not revenue maximization of a spherical cow.

What does that have to do with the revenue claim being questionable?

Also, if that was the goal, wouldn't it be better to tax (or break up) the corporations rather than the shareholders? It comes out of their pocket either way, but forcing asset sales has a lot of negative consequences and bad incentives. On top of that, it handles the problem that the CEO of a huge company has too much power regardless of what percentage of the company's stock they own, by reducing the size of the company rather than their ownership stake in it.

I prefer the phrasing “more liquid and efficient allocation of capital” over “wealth redistribution”.