I get the impression that the Chinese government constantly violets intellectual property of American companies. I'd have no problems if the US government copies DJI designs for military purposes. Return the favor.
The basic stabilization work was done in American universities (Stanford 2004 to be precise), so I think it is more of a value proposition (mass produced, cheap).
Replying to this thread as a whole. I talked to a General in the army netcom a week after that ban, specifically, I was presenting on the commercial drone market uses. At the time of the ban, the army indicated that they had several thousand DJI drones grounded by that order.