I think it was Charvarius Ward* who said it and IMO was correct - if you don't wanna go, then address that pregame. Everyone has lives outside of football, it's fine to have a personal issue that's affecting you - only human after all. But the general sentiment I'm hearing from current and former players alike is that once you suit up, once you put on your pads and your team's jersey you're basically saying "I'm here and I'm committed and I'm ready to go". I hope Campbell is doing well personally/off the field but at the same time I have no doubt whatsoever if he'd went to Shanahan before the game and just said "I'm going through some stuff and I don't think I'm going to be able to go today" that coach and the rest of the team would almost certainly be totally understanding of that. As it stands though it comes off like "I'm healthy enough (mentally, physically, emotionally) to play today...at least I was until I was asked to take a reduced role and play backup" that really rubs people the wrong way I'm sure
*(And he would know better than most, having missed much of the season following the loss of his 1y.o. daughter a few months ago)