WH, your answer sounded like a typical, generic lefty sound bite, hence my reply.
The rest of it is simple, Before we invaded, the bad guys had some basic labs set up in A-stan, trying to weaponize various bad things. They were dabbling with both chemical and some real simple bio-weapons. The area was stable enough for their needs, with a low likelihood of their being interrupted by outside attack.
When we leave A-stan, the bad guys will probably move back in and set up shop once again. When we're gone, there is little chance that they will be interferred with, giving them a greater chance of success at developing long term.
None of this has anything to do with building AKs with files.
All of this information is readily available on the net.