Service of the Kohen Gadol: As A King
In the song that describes the face of the Cohen Gadol when he finishes the service we say that he “Wears the crown of the king.” He too, on this day, represents the entire nation. It is he who recites the confession for the entire nation . The Talmud even compares his confession to that of David . It is he who brings atonement to everybody. When he stands in the Holy of Holies he becomes one with God. He uses that connection to bring atonement to all of Israel.
The description of the Yom Kippur service in the Machzor begins with the story of creation, Adam and his sin. The Yom Kippur service is intended to bring atonement to all creation all the way back to Adam.