Actually most of them moved to Kazakhstan. Iran had a nice hash rate before the China ban. In fact during Trump era Iran included bitcoin in their annual budget to be used for imports/exports too but everything about Iran's international trades is kept under wraps (unless it is with another sanctioned nation or China) so we don't really know the real values.
By my estimates according to some reports of energy consumption and the taxes, I believe Iran currently has a little less than 20% of the total hashrate and that is growing fast.