That's what Magnus is to the "general audience" with regards to chess, and it's going to take a lot for Magnus to be a net negative to chess. We are only making drama because Magnus is so good. Nobody would be blinking an eye if I failed to show up to a tournament, and my opponent would be glad to reap the points.
Not really, at all. That TV series and the COVID pandemic have way more to do with current chess popularity than Magnus & Nakamura. The playing public doesn't really care who the champion is, they play with themselves and only very few follow every game on major tournaments. As a spectator sport, chess is beyond boring, even worse than baseball (seriously, how come people in the US are so into watching baseball??!)
So is cheating. At least this is blindingly obvious.
In the few high level tournaments that are knock out or Swiss system it would be less unsportsmanlike because in those most other players won't have to play Magnus.
Losing games on purpose is unsportsmanlike. Now, if Magnus has good reason to believe that he's just countering bad sportmanship with his own brand of it, that could perhaps be justified in some circumstances. But to the general audience, it makes chess look really bad.