>>716399858
It got it's "legitimacy" due to the lie and forgery of Donation of Constantine and failed to suppress the most devastating and largest heresy Christianity ever faced.
It's main population are mostly Germans, and it didn't even hold the city of Rome for the majority of it's existence, robbing the chance you can call it Roman in the most literal meaning. Made all the more redundant when actual Romans and their successors lived in the Eastern Roman Empire.
It was an empire, but a mostly disfunctional one.