The Afghan Ambassador to the US was on CNN today and gave more information on the fight against ISIS in these underground cave and tunnel structures:
Afghan ambo to U.S. @hmohib on #MOAB & ISIS: Their hideout was the main target and now they will have to surface https://t.co/dkBUakrs88
— CNN Newsroom (@CNNnewsroom) April 14, 2017
In short, Mohib said that in the last week there was a joint operation to clear that underground area, but ISIS had mined the caves heavily with IEDs.
I think that would explain why the US used a concussive pressure bomb on the complex, to explode the IEDs and collapse the cave network.
As Mohib points out, it was their hideout that was the main target. Now they have to surface and thus will be easier to track.
So basically we just drove the cockroaches out of the darkness and into the light.