First off, the idea that a "rich businessman" man in Iran can have 18.5 Billion in assets is so BS, that even some of our stupid minded, corrupt hezbis that we have on ISP cannot defend it.
The corrupt officials are worried about their assets being frozen by countries, just like what happened in the UK. They are trying to bring the money back to Iran before the same happens. The problem is that Turkey will probably release it given how much free oil and gas they get from Iran