Question

why did Charlemagne need the church's?

Answer 1

to priis the lord im dumb

Answer 2

Charlemagne did a number of things to benefit the church; that was in fact essentially the main "achievement" of his reign. IIRC the Lombards were already subdued before his reign by an earlier Frank. But Charlemagne forced the Saxons to accept christianity and killed those who clinged to paganism. He aided efforts to train/educate priests, fought the Muslims in northern Spain, and helped the pope become independent of the byzantines. Lastly, when Charlemagne was crowned holy roman emperor by the pope, he let the holy joe crown him, a kind of acknowledgment of, or acquiesence to, church supremacy over political leaders in the medieval period