Yeah but it's the squad management aspect. The squad building. We as fans all knew that if de Gea is fit and in form, he'd start. Henderson only stayed on the basis of being the #1 goalie. Not #1 unless de Gea recovers form. Ole told him he was #1. He wasn't.
Lingard had the loan, had offers to leave, but was told he'd be used. He of course, was not. Of course the players should take some blame for lacking common sense and being unable to see what is clear for everyone else (van de Beek right now is suffering the same issue). But as a manager, you have to be clear and honest with your players and what their roles are, otherwise they'll get pissed and become disgruntled and cause dressing room issues. Motivation drops, training performances drop, and that attitude just exploded everywhere else once it slips in if not handled appropriately.
That's all on Ole. How he accumulated the squad, the promises he made, and then refused to actually use them as he said (whether he was right to leave them out or not doesn't matter, he shouldnt have promised them these roles). That's the problem with overly big squads and it happens always if a manager collects too fat of a squad. That's why Pep loves working with a tiny squad. That's why he let Jesus and Zinchenko leave. Its better to let them leave if they want regular football, than to force them to stay "just in case" there's an injury crisis.