Young87 wrote:
US is one of the very few countries that do tax their overseas residents. That´s why some give up their American citizenship if they live permanently in another country (like Tina Turner). So yes, Duplantis pays taxes to both countries.
This is untrue.
I'm Swedish and have lived in the US. American citizens are, with certain limitations, liable for taxes and declarations in the United States even though they live and pay taxes in other countries. However, Sweden's tax agreement with the USA means that tax must not be paid twice. Mondo still has an obligation to declare income to the US tax authority, even though that US tax is not paid.