Answer:p
Because if a professional in the military is chief of all the military then no one will be able to stop him if he wants to destroy the country.
Step-by-step explanation:
If you have learned history, you will definitely hear the word Absolute Power. If you let someone professional in the military hold all the military, then if he wants to destroy the country, no one will be able to stop them. But if the President is the chief of the army and he wants to have Absolute Power, he can't because there are professional commanders that can stop the President's Power.