Any country with a nuclear program and ballistic missile production is perpetually weeks away from a nuclear weapon. If they wanted to, Japan, Korea, or Poland could speed run a nuke but nobody worries about them because they fall under someone else's nuclear umbrella comply with international inspectors. Neither of those things are true about Iran, add onto that the Iranians have every incentive to build one. They've already been proven to have enriched uranium well above anything usable for civilian purposes. There isn't any hard proof that they've built a nuclear weapon but nobody wants to give them the benefit of the doubt when they purposefully obstruct and hide things in ways that even Russia and China do not. There's zero reason for them to expel IAEA inspectors unless they were hiding something. Submitting to inspections would also give them irrefutable, credible proof that they're not building weapons and yet they still don't.