Why ONE?

Zion not to be redeemed by committee, the Priesthood is not to be instructed from below. The Priesthood may seek council, and there may be counselors, but the decision belongs to the Priesthood, and there is never but one on the earth at a time, saith the Lord:

7 And verily I say unto you, that the conditions of this law are these: All covenants...that are not made and entered into and sealed by the Holy Spirit of promise, of him who is anointed, both as well for time and for all eternity, and that too most holy, by revelation and commandment through the medium of mine anointed, whom I have appointed on the earth to hold this power (....and there is never but one on the earth at a time on whom this power and the keys of this priesthood are conferred), are of no efficacy, virtue, or force in and after the resurrection from the dead; for all contracts that are not made unto this end have an end when men are dead. (D&C 132:7)

"If Joseph (the Lord's anointed) had a right to dictate me in relation to salvation, in relation to a hereafter, he had a right to dictate me in relation to all my earthly affairs, ... If he did not have that right, he did not have the Priesthood of God, he did not have the endless Priesthood that emanates from an eternal being. A Priesthood that is clipped, and lacks length, is not the Priesthood of God; if it lacks depth, it is not the Priesthood of God; for the Priesthood in ancient times extended over the wide world, and coped with the universe, and had a right to govern and control the inhabitants thereof, to regulate them, give them laws, and execute those laws. That power looked like the Priesthood of God." Jedediah M. Grant; (Journal of Discourses, 26 vols., 2:, p.14)

One, not many heads. The Kingdom of God is led by one head, not a cacaphony of a hydra in Babylon, saith the Lord.

"One Lord, one faith, one baptism", ONE like unto Moses, not many.