A great thing about legends
You get to choose from lots of potential realities. Of course, the bad thing is that once something is declared a legend it it likely to always remain so.
My favorite version of the Camelot story is the Roman connection. When Rome abandoned the British Isles a legion remained behind and Arthur was, or was descended from, the Commander. It is easy to project his officers or their descendents as the Knights.
There is a ton of material out there that speculates wildly.