How did Charlemagne become emperor?

"...In 768, when Charlemagne was 26, he and his brother Carloman inherited the kingdom of the Franks. In 771 Carloman died, and Charlemagne became sole ruler of the kingdom. At that time the northern half of Europe was still pagan and lawless. In the south, the Roman Catholic church was striving to assert its power against the Lombard kingdom in Italy. In Charlemagne's own realm, the Franks were falling back into barbarian ways, neglecting their education and religion.

Charlemagne was determined to strengthen his realm and to bring order to Europe. In 772 he launched a 30-year campaign that conquered and Christianized the powerful pagan Saxons in the north. He subdued the Avars, a huge Tatar tribe on the Danube. He compelled the rebellious Bavarian dukes to submit to him. When possible he preferred to settle matters peacefully, however. For example, Charlemagne offered to pay the Lombard king Desiderius for return of lands to the pope, but, when Desiderius refused, Charlemagne seized his kingdom in 773 to 774 and restored the Papal States..."

His ability to establish a government across the realms of Europe that were easily conquerable, was lead by many campaigns and conquests. His family was also of respectful noble blood, increasing his like-ability to the people under him.