Or more likely just didn't want to fight or were scared.
After the Iraq invasion and "rebuilding" effort joining the army was (as is the case in a lot of countries, including parts of the U.S.) often the only job they could get.
They aren't massively well paid, their leadership was, as I understand it pretty poor*, and their training not great.
Guess what happens when you put a poorly trained army, with bad leadership, no real wish to be in the army up against and armed force that appears to have better leadership, better training/more experience at fighting, no real fear of death and a reputation for being brutal?
The average solider in that army isn't likely to hang around, especially if they see their leaders high tailing it out of there, they're likely to think "well gosh, I'm not remunerated enough to stand here and attempt to halt the advance of the enemy whilst my commander is making a strategic withdrawal to the nearest coalition base".
It's the sort of lesson many armies learn the hard way, hopefully before losing the war.
*I think there was a lot of political appointees and nepotism in it despite what the coillition tried to do to stop it, and like pretty much every Western army up to the 19th and 20th century paid the price for it.