I don't think Chavez threw the fight per se. I think he tried to box him from a distance but was unsuccessful and didn't have a Plan B and became content to go the distance after the first three rounds.

He should have known fans would revile him much more for that than if he opened up, went for the stoppage and got stopped himself. Of course, maybe he couldn't bring himself to endure the punishment of such a fate after tasting Canelo's power. Canelo and countless other boxers would not have hesitated in going for the win, hopeless as it may appear, rather than coasting to a decision loss.