Iran apparently prefers escalating warfare to defeat by sanctions. Salafi Arabia's war in Yemen gives Iran a way to do this without starting a new war.
This reminds me of the sanctions the US placed on Japan in 1941. The sanctions, in that case, were intended to make Japan stop conquering China — a morally valid reason.
Japan had the choice to fight the US, be defeated by the sanctions, or leave China alone. It chose war, and was defeated anyway. The cost of that war was tremendous.
The US has no valid reason for sanctions against Iran. The valid goal, avoiding a nuclear-armed Iran, was being achieved by Obama's non-nuclear deal.