In "morte d'arthur", how does the series of events make the ending of the tale seem fated?

Note, the end of the novel is fated ... the novel is based upon fate, as several of the novel's character's lives are predestined to certain accomplishments or ends. Examples of this can be found in Arthur, who was fated to bring peace; Mordred, who was meant to destroy both his father and his father's kingdom; and Galahad, who was fated to discover the Sangreal. Merlin's prophecies foreshadow most every aspect of the text, and yet, as readers ... we still wait to see if fate can be changed.