The regime's primary goal now is political survival.
U.S. war crimes do not mobilize much public opinion, and thus elicit almost no negative reaction from elected officials.
For Washington’s part, this is a strike aimed at showing Iran that its mimicry with the phantom militias is not working.
Trump says he believes the US drone could have been shot down by mistake, by somebody who was "loose and stupid." What would really be loose and stupid would be to illegally bumble into war.