I was reading about the break-up of Charlemagne's empire, and I was wondering why the imperial title was vacant for the 38 years between the death of Berengar and the coronation of Otto I. Lothair, Louis II, Charles the Bald, Charles the Fat, and Berengar had all used the titles "king of Italy" and "emperor of the Romans," but Rudolph II of Burgundy, who defeated Berengar, only took the title king of Italy, and not the imperial title. Why didn't Rudolph or any of his successors until Otto I use the imperial title? Did the Pope not want to crown any of them?