This would be a lot more concerning if it wasn't widely known that Israel also illegally holds nuclear weapons of its own and therefore should have been sanctioned by the US for decades. Not having nukes is how Iran got here in the first place - the POTUS unilaterally withdrawing from their agreement and bombing them in the middle of negotiations. For all the portrayals of the Iranian government as "lunatics" over the years, getting to nuclear ASAP is the only logical move for a country in Iran's position - just look at how the US went back on its sabre rattling against North Korea once they demonstrated nuclear capabilities.

You don't have to think the Iranian government is in any way "good" but there's literally no logical reason for them not to desperately try to get their hands on nuclear weapons at this point. They have no reason to trust the West to ever follow through on any promises again.