We absolutely could do things if society as a whole agreed to. Billionaires only exist because we let them exist. The only thing stopping us from taxing all money over a certain amount is us.

Unfortunately, I have little faith in our ability to convince people that we should massively step up our taxation. We can't even get billionaires to pay the percentage of income tax that they're theoretically supposed to pay. How are we supposed to convince enough people to go above and beyond?

A huge number of people somehow have the idea that billionaires deserve this money. Or that just because their wealth isn't cash means we can't take it away.

If they try to leave to another country, arrest them for tax evasion and seize every asset they have. Don't let them do any business in the country without paying their share. Get other countries to band together on this until there's nowhere for them to run except shitholes. Even if we can't stop them from being rich in Ireland (and on that note, we should punish tax havens with sanctions), we can stop them from using their wealth to affect other countries.