I think Monty Python is a really great movie! It definitely seems like the writers were trying to critique the chivalric codes and figures of that time. They mostly do this by mocking the things chivalry valued with exaggerated circumstances. One scene that I thought was really funny was when God yelled at Arthur and the knights for apologizing, groveling, and averting their eyes while talking to him. Also, every time Arthur tried to pray to God to thank him for a victory, he would get cut off. In a lot of our previous texts, the knights are very concerned with being humble and fearful of God. Their quests are driven by their desire to please God and fight for his glory, but in the movie, God is only slightly concerned with them. Plus, Arthur and the knights don't even get the Holy Grail; the task God gave them. The movie ends with everyone getting arrested by "modern" people. They're failures! The writers of Monty Python are basically saying "These guys took themselves and their quests way too seriously and we're going to make fun of them for it!" This is more than likely why they chose to satirize King Arthur. It's a story a lot of people know and it's was a long time ago. It's a good way for someone to critique the ridiculousness of systems of power that take themselves too seriously without the reader getting trapped by the details of a more relevant system.
I really like the connection you're making here between the critique of the system and religious chivalric devotion. I think you're right that these things must be connected and--fascinatingly--it raises questions about the relationship between devotion to God/religion and power in chivalric stories. In what ways do you think was religious devotion also bound up with "the ridiculous of systems of power" in the original stories?