Why did Charlemagne take his crown away from the pope and put it on his own head?

Charlemagne took the crown from the pope and placed it on his own head during his coronation in 800 AD to assert his authority and independence as the ruler of the Carolingian Empire. This act symbolized that he derived his power not solely from the church but also from his own achievements and legitimacy as a leader. By doing so, he established a precedent for the relationship between the church and state, emphasizing the idea of a divinely sanctioned ruler who was not subordinate to the papacy.