How did Frankish rulers such as Charlemagne gain control of western Europe?

Charlemagne, a very powerful and efficient Frankish Ruler, had a strategy he used that never he used and never failed him. Charlemagne would go out once a year, go into battle with one of his enemies and then one the opponent has been defeated, he would take over the land and make friends with the people and surrounding areas.

Charlemagne was also well known across Europe too, Pope Leo III noticed Charlemagne skill as a warrior and called for his help. Twice the Franks under Charlemagne's Rule helped Leo defeat their enemies. Out of gratitude, Pope Leo named Charlemagne the Emperor of the Roman people. The people believed that the Church and the Gods were on the side of Charlemagne which gave him the support along with the power to occupy the majority of Europe.