Biologicals are too technical. These knuckleheads have been playing with chemicals for years. What they are finding is that you need to know what you are doing, and have the facilities and technology to not kill yourself while mixing up this stuff. It is a lot more complicated than it appears. As pointed out by rbg81, it is likely they dropped the chemical attack because their tests did not go well.
That is the reason you are seeing more creative ways to secret explosives on planes. The underwear bomber is a prime example. Look for them to shotgun security to get a few through to carry out their mission.
we didn’t think they could develop nuclear bomb capability in the third world either—and it takes a lot more sophisticated technology than biologicals.
To me, it is whistling past the graveyard to think that over a number of years they couldn’t manage to develop or buy some bio-warfare or chem warfare capability. Maybe not in the caves of Tora Bora, but in a lab in Pakistan.
Remember the old adage about an infinite number of typing monkeys will eventually come up with Shakespeare.