Answer: It joined the Church and political power, which created a strong empire.
Step-by-step explanation:
In the year 800, Charlemagne was crowned Holy Roman Emperor by Pope Leo III in recognition of his service to the Papacy including restoring the Pope to the Vatican after the revolt of some Roman Nobles.
The Pope saw this as an opportunity to be protected and for the Church to be powerful once more and so when he proclaimed Charlemagne as emperor, he essentially joined the church with political power which gave the empire a degree of legitimacy it did not have before and established it as a strong empire.