Not sure why ESPN is making such a big deal out of a backup replacing the starter in the 4th quarter of a 41-7 game.
If the score was the other way around then the story line would have been about running up the score, and placing the starters in harm's way. (Though nothing of the same will ever be said about KC's starters, of course.)
Of course the answer to the question of why this is even being brought up is simple: controversy sells. Expect the world wide leader to have a week of scripted debates on this non-story.