Reb Eliezer-
Before there was a treaty Iran was under crippling sanctions. I don’t know the exact details (you can easily look them up if you want) but they were limited in the amount of oil they could sell and which international banks they could do business with (amongst other types of sanctions).
Weather Iran kept its part of the deal is up for dispute. Regardless of that, they publicized that in the meantime they were developing other types of dangerous weapons that didn’t violate the terms of the treaty. It was pretty clear to me that once the 15 years were up they were going to continue on with the development of nuclear weapons- with the added benefit of the billions of Dollars now available to them.
By pulling out of the treaty the sanctions go back into effect (again, I’m not sure to what extent- you can look up the huge amount of sanctions on the State Departments website).
If companies aren’t allowed to do business with Iran and they can lose their ability to do business within the US if they are caught, they’ll be very hesitant to engage in any commerce with Iran. If banks can’t hold money for Iranian accounts and businesses or process transfers for them (or those that do business with them) it will be very unpractical to use the billions of Dollars available to them.
As Dr. Hall correctly pointed out earlier on, now Iran has the money and can continue with the enrichment of uranium. It’s not as easy as he made it sound.
If you had $1,000,000,000 in cash but were under sanctions with no person, business or bank allowed to engage in commerce with you- you may be able to disguise yourself and buy groceries or a prepaid cellphone with cash but you wouldn’t be able to get a credit card, travel or open a business.