He had to pay an exit tax on all his unrealized gains at the moment of rescinding citizenship, so it's almost certain that his taxes were much higher if he did so last year.

Details please, or it didn't happen.

Just for your own information: tax avoidance is legal and expected. Tax evasion is criminal and can result in prison. The distinction is that tax evasion is when you misrepresent the facts in your tax filings.