Paul said in Colossians 3: 17 "And whatsoever ye do in word or deed, do all in the name of the Lord Jesus, giving thanks to God and the Father by him." and I suppose that all of us know that "in the name of" means "by the authority of". So there should be no question as to the who.
Yet, those who would consider themselves Christians, are torn into numerous divisive shreds and simply because far too many take authority upon themselves when Jesus has not delegated it thusly. We can start with the apostasy of the church in the first 3 or 4 centuries. The words of Jesus and the Apostles are the same today as they were then. And no one can find authority spoken, implied, inferred or any other way for the elevating of one elder over another, or placing one over more than one congregation, and certainly not the naming of one as the head of the church. All of this apostasy came about simply because someone assumed, or usurped authority over the Lord Jesus.
And man has continued this "usurping of authority" down through the ages. Starting organizations they call churches and naming them for men, methods, etc., adding their own thoughts to the will of God as binding upon others. And within the brotherhood, the same is true, some have added instruments of music, elevated certain members over the others, installed women in positions of authority, and on and on. Anytime we do anything that gives glory to any man or anything, other than God and His Son, we are in a "heap of trouble."
We have a number of sound brethren who are far more capable of explaining this feature than I am, so I am including some good lessons from several on this subject.