The administration supporters tend to believe that sanctions will end the Iranian nuclear weapons program. That seems an unrealistic opinion if one examines the North Korean case for comparative analysis.
North Korea has endured numerous sanctions and privations in part to build nuclear weapons able to attack western allies or at least lever them. Iran seems to be doing that too; knowing that in time it will get the goods along with excellent missiles to become a regional powerhouse. The recent Iranian attack on Saudi Arabian oil fields may have released soot and smoke harmful to placentas and upset oil investors a trifling moment, yet they also demonstrated the Trump administrations inability to wage a retaliatory strike.
President Trump too often mentions nuclear weapons and tens of millions dead in hostile countries if we wanted to, yet does nothing conventional because he has no clue about how to use military power effectively. The President is going against the walk softly and carry a big stick axiom of Theodore Roosevelt that is usually good policy advice.
US administrations use sanctions when short of solutions to appear to be doing something. When they leave office the situation usually remains the same.
Iran can get help from a variety of sources to muddle through the time it constructs nuclear weapons. perhaps it already bought a few from Kazakhstan at the end of the Cold War during the 90s.