Which scriptures explain that after the last apostle dies, the authority over the church would be the church itself, in other words when did the church change from a theocracy to a democracy?
Now that being said Christ is the head and the Holy Spirit as the Comforter has given us scripture placing things in order. Notice this in Acts 6:2
Then the twelve called the multitude of the disciples unto them, and said, It is not reason that we should leave the word of God, and serve tables.
Seems the 12 (Apostles) told the people to vote on the deacons, to select them, they didn't select them. The principle was set for the membership to make certain choices. The Pastor was to guide the flock as the under shepherd in spirtual traaining. The Apostles faded out and with the death of John ended, in the 2nd century. For no one since that time can claim to have "seen Jesus Christ our Lord"as the disciples, early Christians and Paul says he did in His ressurection body.