Their state religion which worships the devil uses the current imperial family's name to cement its power this was made possible because the devil made a deal with the first emperor which turned his and his descendents hair blue, a sign of their contract, and if that symbol remains worship will continue, giving the devil power(they way it's explained is worship=power)so they need a new emperor so they can completely remove the church and it's influence. The count is the devil's human form and is only active cuz it's worship is dwindling bc of the mc which is why their obsessed with her. That last part iant known to the imperial family which is why they're trying to turn the count into the new emperor even though hes the devil. :)
misspelled some things my bad T_T
If the demon blood is in count axios then why is royal family need to be removed