No one will admit anything, but Stuxnet appears to have been a joint American-Israeli operations. The Iranians believe this as well, and are very angry over having been attacked and damaged in this fashion. But they can't admit it, without looking weak to the Iranian public.
Rather than trumpeting an American and Israeli attack (the Holy Grail of Satanic enemies from Iran's point of view) to rally the people,the Iranian regime fears that it would make them look weak if they admit they were attacked! You'd think that the mullahs would welcome a chance to rally their people. But this was an effective attack on Iran's nuclear facilities that Iran could not stop.
I've long thought that only ineffective force rallies an enemy population. Effective force can make regime opponents hopeful that the foreign help will help them achieve their goal. If we spent weeks crippling Iran from the air, which the Iranian people could see are not being resisted by the Iranian government, might not that make them look weak? As well as actually weakening them? Keep in mind all the propaganda announcements that Iran makes of new wonder weapons that never turn out to be more than mocked up crap; or their exercises with scary sounding names (Operation We'll Smite Your Infidel Asses With the Courage of Our Death Wishes!) that use silly weapons or rely on photo-shopping images. They project the image of strength that effective military force would shatter.
The idea that force just rallies the enemy is largely drawn, I think, from the image of our cruise missiles striking mostly empty tents in Afghanistan after the West African embassy bombings by al Qaeda. If appearing weak is that scary for the mullah regime in Iran, by all means make them look weak.
And if time reduces our options to striking or hoping we can deter Iran, who can believe that striking Iran despite the risk of rallying Iranians to the regime is the only hope of protecting us?