Quite simply, the sum is less than the parts.
It’s either a locker room issue (no drive and leadership, no one to grab the game by the scruff of the neck) or a training ground issue (individual errors due to lack of training on situational play)* or a lack of trust in the manager’s tactics, but the players seem to “know” that no matter what they do, either someone else will make a dreadful mistake or, if they make a mistake, there won’t be anyone there to help them out. And even if they play well enough for 20, 30, or 40 minutes, the mistake(s) will arrive soon enough.
*could be each and all of these issues