I think that, whoever else is to blame, whoever in the Iranian military or government decided to refuse the Air Defence Unit's request that the airspace be closed during the heightened alert really has some explaining to do.
On the face of it, it seems an act of criminally irresponsible recklessness. And then cynically lying about it until the military, quite rightly, could contain their anger no longer, and went public ... that's utterly wrong.
I keep on thinking, too, about what the poor missile controller who actually fired the missile must be going through, since he (I assume it's a man, in Iran) had clearly been put in an impossible position by his superiors -- it just doesn't bear thinking about.