A “win” for Trump. He may never even have truly intended to retaliate in this manner, but by publicly halting such action provides a nice optic of patience and consideration to win allies, perhaps in UN support against Iran.
This is exactly what I think. Trump is a master of politics and optics. I think he launched that attack with the full intention of halting it to make himself look like the more reasonable party, while still sending the message to the Mullahs that he can hit them.