If I was Iran, or any country on the US's naughty list, I would be trying to build a nuke as quickly and quietly as I can. It seems to be the only way to not get bombed.
Given the track record in the region and the relationships involved, not getting a nuke seamless will lead to getting bombed with almost 100% certainty over a long enough period.
If they botch the quiet part, they'll almost certainly get bombed in the short term, which may or may not lead to the end of the project. But then will almost certain prevent getting bombed more in the future.
