Symbolism is a figure of speech used for when an author wants to create a certain mood or emotion whilst writing a book or a novel.
That is a very controversial question. First of all, King Arthur was a king, not a knight. And if you mean who crowned King Arthur, then that would be his followers. And if you are referring to some point before his kingship, then it could be the Lady of the Lake, or Merlin. It all depends on which version of the story you mean, because there are hundreds.
