Come on, you know better than that.
Simply put, "Vicar" is a term which means "one who acts in the person of another." After the Ascension, Peter represented Christ as Head of the Church. The successor of Peter, the visible Head of the Church is, therefore, called the Vicar of Christ because he is the representative on earth of Christ, the invisible Head.
Christ's words to Peter (Matt. 16: 18,19) constituted a permanent office in His perpetual Church. That office was to be filled by whoever succeeded Peter as Bishop of Rome which was the official bishopric of Peter up to the time of his death.
As proof that Peter's office passed to his successor, and not to the other Apostles after his death, we have the facts of history.
Unless the primacy of authority were conferred on the Pope by Christ Himself, we may be sure that the bishops and other prelates of early Christianity never would have submitted themselves to it.