Why was Charlemagne not truly the emperor or the roman?

Charlemagne was not truly the emperor of the Romans because his reign lacked the political legitimacy and continuity associated with the ancient Roman Empire, which had effectively collapsed by the time he was crowned in 800 AD. His title was granted by Pope Leo III, which established a religious foundation rather than a direct continuation of Roman authority. Furthermore, Charlemagne's empire was largely a Frankish kingdom, and while he sought to revive Roman culture and governance, it was fundamentally a new entity rather than a restoration of the Roman Empire. Thus, his rule represented a blend of Germanic and Roman traditions rather than a genuine revival of Roman imperial power.