I was watching something on tv a couple of months back about MA. They did an interview with the guy that teaches Gracie-JJ in the army. The jist of his comments were that no martial art is really usefull since wars are fought with guns and bombs and whatnot, they teach them for the qualities that they(MA) develop. I think their choice of art is greatly influenced by popular opinion and simplicity of the art.
You basically hit the nail on the head, becasue One guy liked it he managed to convince the right people that this was the way to go. His Name is SSG Matt Larson. I know him and have talked with him about his decision and the various merits and demerits of the arts. And for what he was trying to accomplish GJJ seemed the appropriate fit.