If Putin is no longer the leader of Russia, then having wealth outside of Russia is very useful. That can be because he had to flee or for his family. Obviously it has to be hidden, so the assets are not seized by other countries due to sanctions against Russia. So it has to have a financial manager, so sign necessary paperwork at least. Epstein can be easily blackmailed, making him easy to control. However he is certainly not the only one. Putin has the wealth of Russia, so stacking away some millions is pretty easy.