I've wondered for some years (and never read it anywhere reputable) whether the memories of Alfred and his struggles against the Danes were metamorphosed by the 11-12th centuries in a memory of a great English hero who fought for his nation against foreign invaders . . . but since so many Danes lived in England, it was moved back in time, to vague references in Gildas and others, and "stuck" on the character of King Arthur. There are so many similarities between the military situation there, and many in the character of Alfred, ... of course, nothing quite explains Guinevere, Lancelot, et al.

But at least I suspect the long-lived affection of the English for the House of Wessex played its part in fleshing out the Arthurian cycle.