Could be any number of things. Unlike western nations that have a tradition of the military being under the control of the civilian government, in china the military sees itself as an independent, co-equal, branch of the government. Which has led to any number of internecine power squabbles in the past, in which the Central Committee has said, "Do this.", and the PLA/PLAN/PLAAF have replied, "No." And since they have the guns...