Letting Marouane Fellaini's release clause expire in the belief Everton would accept a lower offer.
"But can't Everton just accept a lower offer anyway?" "But won't they value him higher than that, considering the amount they paid?" "But won't that leave him no time to settle in to the side?" "But won't that mean United will have to face the early difficult games without him?" All reasonable questions asked when this plan was mentioned in the press, all assumed to have perfectly logical answers.
We've seen decisions in recent years destroy clubs, cause untold damage, and ruin the reputations of good men. This ended up with a very wealthy club having to pay a few million extra. But it's the sheer simplicity and obviousness of the incompetence involved that is absolutely unparalleled here. Never again doubt how idiotic very wealthy men in positions of great power and influence can be.
Annoying Athletic Bilbao and screwing Ander Herrera
Athletic Bilbao are a difficult club to deal with. If the proposed move is at all hostile, they can obstruct and make things difficult. After all, they can't simply go out and buy anyone, so money is rarely of huge concern to them. They are, in other words, a club you don't want to be dealing with on deadline day while pushing in underwhelming bids. Especially when you then refuse to pay an amount more or less equivalent to what was lost in the aforementioned Fellaini fiasco.
Yet the most galling thing about the pursuit of Ander Herrera was that the midfielder seemingly really, really wanted to play for United, reducing his wage demands and putting up some of his own money to make the deal happen. This to facilitate a move away from Athletic Bilbao, a place it's not easy to leave either emotionally or, apparently, legally. The club are said to "still like" the player. If it's reciprocated not it'll be a miracle.
The €40m Sami Khedira bid
If it's true, then in a way it at least shows that United tried. It will also show that their best is a long way from good enough. Unless we're to believe United's plan all along was to do nothing for months then bid silly money for Khedira at the last minute, it was a very loud, anguished cry to let the world know that something had gone terribly wrong and the club were in full-on panic mode.
Not keeping tabs on Mesut Ozil
"Nah, you're alright" were the words to which effect United refused to sign Mesut Ozil, leaving him for Arsenal to have their wicked way with him. Later on that day, United had managed to make a mess of the Herrera transfer and desperately wanted more reinforcements. If they were prepared to offer €40m for Sami Khedira, they probably could've paid a little bit more to get Ozil (the concept of 'surely United will be happy to pay a few million more' being a difficult one to grasp in the more enlightened times of this morning, we accept.)
Alienating the wrong players
Now, Fabio Coentrao is a good player, a fine option at left-back and decent cover in other positions. But left-back ought to have been way down on a list of priorities that included two, possibly three midfielders, an option at left-wing and perhaps another source of creativity further forward. That would've correctly deployed the boots up the rear to the areas in which they were needed.
True, Coentrao is also an option on the wing. But no team has ever won the Champions League playing a left-back at left wing. No team has probably even got to the semi-finals, or won their domestic league. I've not researched that, but I'm pretty sure it's true, just like no other club of that calibre loans left-backs, or uses the transfer deadline day to get their business done. There's a pattern emerging here.
Hiring Ed Woodward
I think we've fairly comprehensively covered his failings above, but David Gill was, for all his faults (and they were many, and any United fans wanting him back rather than, say, someone new who has no record of dishonesty or cluelessness) a very tall man. Probably quite intimidating in negotiations. Ed Woodward, it has been pointed out, looks like the third brother of Niles and Frasier Crane. You don't take a knife, or an unused sitcom character, to a gunfight.