Or just make it 99.9999 once every time there's a new name on the list of eligible payers.

Nobody deserves that many digits in their name. Literally zero people have ever deserved that.

They should have never had it, and that should be a worldwide rule.

That was the narrative in Ma before the extra tax on income above $2M and it ended up raising even more money than predicted.

Right? Where are they going to go? You can't take your real estate with you. You can't pick up culture and move it.

They won't move, this is where they make their money. They need us more than we need them

I don't think the billionaires move because of a 1 time 5% wealth tax, depending on the rules, many won't be able to move in time anyway.
But if the tax is 5% every year, I'm pretty sure most billionaires would. Even if it's not all of them.
But when it's easy to move not too far away and avoid it many will.

Remember most billionaires don't register an income nearly as extreme as their fortune.
If a billionaire pays 30% tax on $100 mil. income, and most don't because of deductibles and outright cheating, then that's $30 mil. in tax.
I they pay 5% in wealth tax on a fortune of $1 billion, that's $50 mil. That would mean the wealth tax is higher than their income tax.
And if they can move almost anywhere else to avoid it they will.

Also the psychological effect of suddenly introducing a high yearly wealth tax would be worse than starting moderately with 0.5%, which my own government in Denmark has suggested they might, and even that the rich threw a hissy fit over. But start moderately, with 0.5%, then wait a couple of years and increase by 0.25%.

It's not that I think this is really fair, I personally think the very rich should pay more for the privilege of enjoying to be rich.
And the money should go to make conditions better for the poor and middle class.

I also very much agree with what Mamdani has done. Because they can't just move away to avoid those taxes on for instance their luxury houses that make a British castle look modest. They can't just move away and then come visit as they please, they would have to actually sell the property to avoid the tax.

Good. Why would we want people who take vastly more than they contribute to remain in our state?

That's a good question, but the rich are good at making the poor fight for the scraps. And their riches may come from the whole of USA and even the entire world, so local states fight each others to keep the rich in their state, because their taxes are still often significant even when they pay to little.

As I mentioned, the best way to stop this is by mandatory international agreement on a wealth tax. But unfortunately such an agreement is not likely. But we should all at least support it.