Because we all know that ISIS is a bunch of techie nerds that can hijack a drone with a missle and fly it to 30000 ft and hit a target moving at 500 mph ... and that is so much easier than getting a sympathetic baggage handler to stow a bomb with an altimeter in a suitcase on board.
I don’t know if it’s true or not, probably not, but it’s possible. ISIS has been under-estimated since they first came to being. What wouldn’t be impossible or even unlikely is that an ISIS sympathizer be hired as a contractor or employee of the facility. Look at all the “rebels” the US trained in Syria who were actually our enemies.