Board Thread:Spoilers!/@comment-11468987-20151019022445/@comment-24674051-20151019155734

And this is Once, where the original stories get mashed up, twisted around, and then presented again under different guise.

Arthur was meant to the ruler of Camelot at the time. but due to circumstances, maybe he is no longer fit to be the ruler, leading to the sword to seek a NEW ruler.