Pepin's Venice

Charlemagne's Empire controlled all of modern day France, and much of Germany and Italy. However, his attempts to take the Italian City state of Venice failed in 810, with his son Pepin dying in the battle. The Crown passed to Charlemagne's second son, Louis, who is noted for being a very bad ruler and one of the reasons for the end of the Frankish Empire.

In this alternate universe, however, Pepin was victorious in the battle of Venice and managed to become the Frankish Emperor following his father's death. Pepin was a much better ruler than his brother, resulting in a stronger and longer-lived Frankish Empire.