This is much better than something a billionaire did, but you don't seem to have linked a source. I found one: https://www.commondreams.org/news/global-wealth-tax-plan
"The proposal aims to incentivize and guide different countries to join the initiative and address policy, administrative, and data deficiencies, ensuring that high-net-worth individuals are taxed more efficiently in line with their wealth," the Spanish government explained. "To achieve this, it is necessary to foster international cooperation in multilateral forums to promote and facilitate the implementation of evidence-based reforms and ongoing experiences regarding the taxation of large fortunes in different countries."
The plan—crafted by the governments of Spain and Brazil and presented at the United Nations' Fourth International Conference on Financing for Development being held in the Spanish city of Seville—was quickly praised by an assortment of international nonprofit organizations as an essential tool for tackling global wealth inequality.
I'd like to see more countries join, but we need a hell of a strategy where I'm at because politicians in English speaking North America will be the hardest sell.