Why is Charlemagne (French king) called great?

He became the most prominent ruler in Western European history during the early Middle Ages, from the fall of the Roman Empire to the Crusades. He ruled for 42 years and achieved many successes:
Defeated the Lombards on the territory of modern Italy, the Avar Kaganate on the territory of Hungary and the Bavarians and Saxons on the territory of Germany.
He defeated Byzantium and expanded the eastern borders of his state to Dalmatia.
He became the first emperor in Western Europe after 476.
Under him, the Carolingian Renaissance took place, there was an upsurge in culture.