they are letting Israel's "preemptive strike" play out to no response so that it can be determined by the onlookers that they are the sole aggressor against Iran.
They are quite literally pulling the "heh, nice punch kid, but now we fight for real!" anime bit for the world to see, to get the moral high ground to attack defensively.
It is all theatre, optics and subversion. Such is the ethos of Semitic Warfare.