Geopolitical context matters. Reagan had to deal with the USSR, which was doing its thing next door to Iran in Afghanistan (IOW, significant Soviet resources were near by). He had to consider whether and how the Soviets might respond. Reagan did play Iran and Iraq against each other in their neighborhood war.
Fast-forward to GHWB, the perilous unravelling of the USSR was happening early in his administration, and then Saddam invaded Kuwait.
Clinton was the first POTUS who had minimal geopolitical complications, but WJC was kind of lazy.
For better or for worse, GWB was dealing with the aftermath of 9/11 and a seemingly renascent Saddam (it appears that Saddam fooled US and other countries' intel agencies into thinking he was acquiring more WMD than he actually had, hoping to intimidate western countries). That might seem to have been the time to smack Iran, but the US was already spread a bit thin, and trying that was probably politically untenable (the "unity" immediately after 9/11 was a MSM-aided Dem sham).
Obama was so bleeping lazy that Iraq was almost lost to ISIS, and the loss of Afghanistan began with Obamian negligence. Obama could have whacked Iran, but arrogantly thought he could buy peace with pallets of cash.
Trump had a Congress who would bemoan oncologist unemployment if Trump cured cancer, and, of course there was Russia, Russia, Russia. Congress would have stopped any effort to whack Iran.
LIEden returned to trying to buy peace with cash, and had populated his MalAdministration with Israel-haters. LIEden could have whacked Iran but there was no way he would have thought of it.
So, yeah, 46 years late, but realistically only Clinton, Obama, and Biden had a reasonable geopolitical and domestic opportunity to hit Iran.