Every half-decent parent learns, before their first kid even starts school, that you can't threaten consequences if you aren't stone-cold ready to follow through.
Nicholas GrossmanTrump has made big threats and given Iran a one-last-chance at least 8 times now, backing off without getting anything every time. "A whole civilization will die tonight" was April 7! He has claimed Iran is making concessions, desperate for a deal, and a deal is imminent too many times to count.