From what I have read in the debates about the 2A was that the anti-federalists were afraid because the COTUS had done something unprecedented in that the Fed took control of the state militias. The antis were afraid that the feds might not sufficiently arm them and so wanted the provision to make sure they could arm them if the fed didn't. The militia had been under state control since their colonial charter and they were not happy about a central government controlling them. Thus the 2A and the right to choose the state militia officers. Since at that time the militia was thought to be the preferred way of protecting the nation and the states from insurrections and foreign enemies the personal right was kind of implicit. That was because the militia were required to furnish their own arms whn called upon. Of course, today that system is gone and so Heller had to decouple the two clauses because of the right of personal self defense.
"God and the Soldier we adore, in time of trouble but not before. When the danger's past and the wrong been righted, God is forgotten and the Soldier slighted."