Final answer:
The crowning of Charlemagne by Pope Leo III was a mutually beneficial political act, which helped to legitimize Charlemagne's power but also led to controversy with the Byzantine Empire. Charlemagne was not angered by the crowning itself; instead, it strengthened his position and allowed for closer ties between the church and the state.
Step-by-step explanation:
The crowning of Charlemagne by Leo III did not actually make Charlemagne angry but rather it was a strategic move that benefited both parties. Charlemagne had previously restored Leo III to his throne, asserting his power over the Pope, and the crowning was a political act that helped to cement Charlemagne's authority and legitimize his rule over his vast empire which spanned across western Europe. The act of crowning also set a precedent for the relationship between the papacy and the secular rulers, although it did stir controversy, particularly with the Byzantine emperors who saw the coronation as a usurpation of their authority.
Moreover, Charlemagne was known for his efforts to revive learning and reform the church, which is now referred to as the "Carolingian Renaissance." His administration closely involved the Church, having used the structure of the Church to govern his empire by insisting on a strict hierarchy and sponsoring education. Thus, the crowning by Leo III represented a reciprocal relationship where both the Church and the emperor envisioned benefits in their alliance, although this did cause tension with the Byzantine Empire.