If rich people would like to preemptively pay more money in to society to stop societal collapse and their own eventual defenestration... I'll take it. There will always be imbalances of power, which we need to effectively regulate and not leave the most powerful to regulate for themselves.

Nah, they leave the lobbying to their employees or front organisations.

This. It's all performative. They know that they have the politicians in their pockets and there's no chance of new taxes targeting the wealthy. They will lower taxes on the wealthy just like they have continued to do for the past 50 years.

Millionaires are closer to being one of Us than they are one of Them. I think some of them know that too.

A. Liquidity B. Leverage C. Interest

Mostly their income depends on already having money. They get paid for having money.

They want it to go out as tax so they can then claim a bunch more on top of their existing charitable donations.

You don't pay tax on charitable donations, and it's a good way to hord off some money if you don't want to pay tax on it, at least until such time as you can relocate your money to a less taxing nation, but there is a limit to how much you can tax exempt in a year. For normal people this limit is irrelevant because it far exceeds the amount of money they would ever get in a year let alone amount they would be able to give as charitable donations.

If there was a millionaire tax they could pay that and essentially offset the tax they pay by reducing their charitable donations. They would end up in exactly the same position as they currently are, but society would be slightly less pissed off with them. All to their benefit.

The only millionaires and billionaires that don't want this other ones that are doing weird dodgy tax things so they don't pay anything. Most of the wealthy 1% do actually pay their fair share of tax (although it isn't high enough) because it's so little money to them that it's not worth fighting about it. Likes of Elon Musk a special breed of narcissist who actually put more effort into not paying tax in its worth.