You could blame B. Hussein and the Democrats for withdrawing from Iraq. You could blame Bush-the-Younger and the neocons for sending American troops there in the first place.
You certainly could blame the Iraqis for handing the town back to the Jihadis. But maybe they really like living in the 7th century CE.
The Marines who fought there, of course, are anguished. As undoubtedly are the Army soldiers who fought there, too, although to much less publicity. As were a lot of combat veterans of Vietnam when the feckless pols withdrew from there, leaving the American dead to have died for nothing.
Well, not for nothing. They died for the Marines, for the Army, for their comrades-in-arms. That might not be enough for their survivors. But, in the end, it’s about all there ever is in war.