The cardinal sin for a professional runner is not to care about the sport.
The worst dopers, for all the harm they do, for all the people they hurt, they're willing to go to extremes with their own body just to win a race. There's (rightly) not a lot of sympathy for dopers on here, but there's a grudging admiration for someone who cares that much.
I'm not saying Athing Mu doesn't care about track. We truly don't know. But with her sparse racing schedule along with all the modeling talk, it leads us to believe that perhaps she's just not that interested. If later this year Mu does an interview saying that track is her #1 love, she knows all Bekele's best times and sometimes posts on these forums under the name "rojo", and her lack of racing is just due to injury/Covid/fear of losing, I predict she'll be more beloved than ever in no time.
I'm also not saying that not caring about the sport *should* be its cardinal sin, just that it is. I think we can agree that it's not a personal moral failing to have interests that differ from your talents. But it's a minefield that people should be conscious of, whether you're a professional athlete or someone in their orbit, or just a forum-reader confused at others' (or your own) sudden antipathy towards Mu. As a person, she's probably wonderful. As an athlete, you've got to demonstrate love for the sport, whether that's fair or not.