The message to all other states to get nuclear weapons as soon as possible is reinforced by Trump's scrapping of the Iran nuclear deal. Even if you negotiate a treaty with the U.S. agreeing to deescalation, a new leader will likely tear it up (given the flip-flopping of the U.S. presidency, which has near total power over foreign policy).

Even returning to the negotiating table isn't enough - the U.S. and its allies may strike you anyways. (as they did last year when they killed the lead Iranian negotiator and again preemptively attacked during recent negotiations)