He is awfully old and sick looking. Heart attacks happen all the time.
However, if he violated certain laws relating to things like human trafficking, I think that certain seizure laws apply. (Laws which in general, I dislike.) This would need to be done openly to remove the money from his control.
Trump’s EOs have already taken care of the possible money-seizing - but Soros has moved his money.
money.cnn.com george-soros-18-billion-open-society-foundations
Oct 17, 2017 - Investor and philanthropist George Soros has moved $18 billion to his foundation — the majority of his estimated $24.6 billion fortune. The Open ...