"The Empire has fallen but God never falls" is the "point of view" that early medieval lords thought, and they did well, because, the "ius Commune" or medieval legal system is the son of the Roman Law and the Canonical law. Without Rome, there was no power containing barbarians of invations, so, the Church and "ius commune" became the rule on all Europe with its variants, with the purpose of standardizing law and having a "European Identity" as Christendom and having ethical standards in the first way of "International Law" Also, just think about this for a moment, You are a Medieval Monarch, and you want to impose a new kind of law or rule, but if you do it yourself, you will be looked at like a tirant, What do you do? easy, you ask the church to say whatever is good for you, that way, the church imposes the law you want to impose, and you don't have to actually write that law, and the people will obey to a God that is always fair and benevolent, or at least, to the representatives. Im an active Catholic, but I have to admit to you, that in this cases and many others, the Church is just an option to have power and control.