I don't think scantions work.
With as many participants as there are in the global economy it makes sense: the sanctioned country can easily change suppliers and not have to change policy.
Prior to the war in Iran, the US had sanctions on Iranian goods, especially oil. Iran has been selling mostly to China. Crude oil is about 56% of Iran's exports.
The point is, Iran still sells crude oil and makes revenue.
(I'm not defending Trump, he scrapped the Iran nuclear deal in 2018 and (re)imposed sanctions on Iran.)