Why was Charlemagne crown on Christmas day in 800 AD by the pope?

Charlemagne was crowned on Christmas Day in 800 AD by Pope Leo III to symbolize the alliance between the Frankish kingdom and the papacy, reinforcing the idea of a Christian empire. This event marked the revival of the Western Roman Empire and established Charlemagne as a defender of the faith. The timing on Christmas also underscored the significance of Christ's birth, aligning Charlemagne's reign with divine authority and legitimacy. This act solidified his power and the church's influence in European governance.