"The wealth of the wealthiest people is a big “share of wealth” but “taking” it is a one-off exercise. Governments could blow through it in no time, and then have no means of sustaining the largesse that they have created an impression of normality for."

Taxation cannot be a source of revenue for a sovereign currency issuer, such as our federal government. It can create a demand for the currency the issuer deems able to pay tax obligations, but the issuer must create that currency before it is available to collect (or borrow).

It can also serve as the "stick" in the carrot/stick relationship governments have with their own currency. By penalizing undesirable behavior in investment with higher taxation a government can redirect its previously spent currency into social/economic improvement that doesn't depend directly on government funding, such as charity and less profitable ventures that serve the common welfare.

Because the sovereign currency issuer always has infinity currency available to spend and needs none of it back to enable future spending (not accounting for inflationary pressure) taxation and borrowing add nothing to that ability. Infinity+tax is still just infinity, Taxing for revenue has been obsolete since FDR ended convertibility of dollars for gold in '34.

The best way to overcome the influence of wealth in our government is to make it irrelevant, not to confiscate it in an unnecessary effort to "fund" what needs no funding. Once the people view the currency as a product of government and law, not business, other reasons to tax extreme wealth will prevail and the wealthy will have little defense against them.