When you killed everyone in a coup, you are by definition a new military. You might prefer less authoritarian system now, but all your friends who are running around with rifles trying to do a coup are in it for power, it's just how the selection process goes, for everyone bright eyed idealist who will immediately relinquish his absolute authority that he just won by fighting a civil war, there will be 10 people who fought in civil war to get this absolute authority.
We know that, because actually I deceived you earlier, it's not 19th century now, and we already saw how that happened. And also, both technologies and situations are different now