Are people making this too hard?
The IRAN deal was just a way to get sanctions dropped so they could do business with Rosatom, Airbus, Siemens, etc.
The US and EU sweetened the deal with cash handouts - directly from the taxpayers with a stopover in Iran, and then into the hands of Russian and US/EU oligarchs.
Iran knows they are just a money launderer. That is their leverage.