I think it has more to do with nukes than oil. North Korea is a good example that once you have nukes, no one can touch you. No one wants more nukes, especially in the hands of IR, in this world.
At this point, every country which has natural resources which the US might want to steal should have nukes.
Except they don’t.
North Korea minds their own business.
When Iran builds a base in Mexico or Canada, we can talk.