United are in this mess because of the lack of quality of the players.
What's happening to United re' this run doesn't usually happen, because most managers aren't good enough to get a squad like this in to the PL in the first place.
If your success in the PL is based purely on managerial skills, team spirit, being on the crest of a wave emotionally and being an unknown quantity, then you're vulnerable.
Those qualities are very good, but they're short-lived, fragile, and not enough on their own.
At this level they need to be backed up by ability, and that's the chairman's responsibility as he holds the purse strings.