I think the difference, and what Carlsen is doing well in this case, is just backing out now instead of trying to defend his title and then getting 5 games in a

I think the difference, and what Carlsen is doing well in this case, is just backing out now instead of trying to defend his title and then getting 5 games in and just going "I hate this and I want to leave. I forfeit". That would look even worse for him, and be unsatisfying for his opponent and the public. In this case, he realizes he doesn't have the passion for this event any more, so he's doing the best thing for the sport and just letting two people who are still passionate about it compete instead of doing the mental-sports version of playing injured.