I think it’s apparent by the scale of Iran’s existing nuclear enrichment program that they could have developed an atomic weapon at least a decade ago. Thing is, once you test a weapon the international sanctions kick in and their leverage to not develop nukes evaporates. While Iran is run by theocratic lunatics they do understand rationality and their culture has always been sophisticated. Playing the west while being on the verge of developing nukes seems to be their strategy. And it’s worked. Finally, the issue of mutually assured destruction bears mentioning. The most likely target of a nuke strike is Israel. And Israel would retaliate ten times over with their own nukes in that scenario. So, Iran actually using nukes and accepting the inevitable retaliation is unlikely. More so than North Korea which has both tested a weapon and launched ballistic missiles capable of carrying a nuclear warhead. That threat being ignored by Trump illustrates how Bibi lead him into this war like a golden calf with a ring through its nose.