the Round Table is shattered from within
The gap between medieval Christianity's ruling principle and everyday life is the great pitfall of the Middle Ages. It is the problem that runs through Gibbon's history, which he dealt with by a delicately malicious levity, pricking at every turn what seemed to him the hypocrisy of the Christian ideal as opposed to natural functioning...

Chivalry, the dominant idea of the ruling class, left as great a gap between ideal and practice as religion. The ideal was a vision of order maintained by the warrior class and formulated in the image of the Round Table, nature's perfect shape. King Arthur's knights adventured for the right against dragons, enchanters, and wicked men, establishing order in a wild world. So their living counterparts were supposed, in theory, to serve as defenders of the Faith, upholders of justice, champions of the oppressed. In practice, they were themselves the oppressors, and by the 14th century the violence and lawlessness of men of the sword had become a major agency of disorder.
When the gap between ideal and real becomes too wide, the system breaks down. Legend and story have always reflected this; in the Arthurian romances the Round Table is shattered from within. The sword is returned to the lake; the effort begins anew. Violent, destructive, greedy, fallible as he may be, man retains his vision of order and resumes his search.

Barbara Tuchman, A Distant Mirror