Players, especially young players, need leadership to help produce a good working environment and dressing room culture. That will help develop their own mental strength and help them react properly when things go wrong.
If you have a toxic culture throughout your workplace it is going to destroy morale and confidence, and cause performance levels to drop. That's true in any workplace, but especially so for anything that requires physical attributes at an elite level. Small percentages are so important at this level that even a small drop in performance levels are massively important.
Jose played a huge part in developing that terrible dressing room culture, spending two and a half seasons throwing players under the bus and going out of his way to destroy the confidence of half his players so he could be 'proven right'. He didn't care about the players, he didn't care about the club, his priority was avoiding as much blame for the problems as he could. And he was more than happy to do this publicly for the world to see (the disgraceful scenes of him deliberately waiting for the media to be there before stripping a confused Pogba of the vice-captaincy on the training ground). Then Ole came in and went to the opposite extreme, blowing smoke up everyone's arse and not actually developing a constructive and strong mentality. Five and a half years between these two, half of some players top flight careers. It's left a group of players who are incredibly mentally fragile, who can look good when things are going well but the instant things go poorly they fall apart.
Some players are naturally that mentally weak. For instance, I'm not sure if even Fergie would have been able to get the best out of Martial. But the reality is that most players will move towards the average of the team. If you drop 90% of players into the mess that we currently have, after a while they will end up looking like they are a problem as well. Rashford is probably the best example - if he'd spent most of his career with a manager and a dressing room that promoted a strong culture and mentality, it's highly unlikely he'd look like the lazy, can't-be-bothered player that he currently appears. Whether it's too late for him to change or if he's now stuck in his ways is one of the more interesting things to find out going forward.
The question is how easily can it be turned around when things have gotten as bad as it has? Personally it's a huge reason I think we need a significant rebuild. Bring in five or six decent players with a good mentality to go along with the new manager, while letting a similar amount of players leave, and it'll allow us to completely reset the dressing room culture. The new manager and players can set the new 'normal', and the players who remain will hopefully lift to that level.
