Either it's the greatest military victory since the Battle of Singapore, when 35,000 Japanese troops capture 80,000 Allied defenders within a few days, or there's a little more to the story.
What appears to be happening is the Sunni tribes and population centers are refusing to fight for Maliki, and instead joining under the ISIS banner. The troops aren't just deserting, they're basically defecting.
And they know Obama and the Iraqi government wont back them. Everyone learned a lesson in Benghazi.