The question remains: occupying all of Europe - what were the Germans thinking?
Not least because they weren’t exactly great about making other peoples equal citizens in the empire, especially in eastern Europe. It would’ve come apart eventually. An assertion without proof, except that prior attempts failed as well, and those were in times where controlling the population largely meant controlling the nobles, arguably an easier proposition. The last to come somewhat close to doing it it was Charlemagne, wasn’t it? and i don’t think it much survived his death.