Having read the initial posts in this thread, it's clear that my opinion on the subject differs greatly from that of @Joshirin.
David Moyes quite simply inherited a poisoned chalice; an impossible job. Believe it or not, I predicted this in an article which was posted in July.
It boils down to the squad he inherited. I won't go into full details (if you want those, read the article). After a rocky first campaign, David de Gea went from flop of the season to one of the best goalkeepers in the league.
The defence was always an aspect that sounded the alarms for me. Last season they conceded 43 goals - the most out of the top four clubs, therefore this weak link was well documented. Vidic and Ferdinand were quite possibly one of the best defensive partnerships that the Old Trafford faithfuls have seen, however they're on the wrong side of 30 along with Evra. This season has further documented this fact; Vidic is off to Italy, fans are split over Ferdinand and the club stuttered and stalled over Evra's contract. A lot of fans pointed to Smalling and Jones however as I said at the start of the season, they have had their own injury problems to deal with and quite frankly, they both blow hot and cold. As for Buttner, he's very rash in defence and has had problems settling into the area; it didn't look like he could replicate Evra's transition to the Premier League, and quite frankly, it looks like he'll be off in the summer if the fans have their wish granted. An aging and injury prone defence was not the best of gifts from Ferguson.
Before the start of this campaign, Welbeck had scored just two goals in 39 appearances. The situation was problematic as it was not a situation where he hadn't been given the chances; it was often his poor final decision and finishing that let him down. One of Moyes' first tasks was to talk Welbeck up in the media, an indicator that he was not going to sign a new striker. Don't forget the Rooney circus at the start of the season, that's now been sorted to the tune of £300,000 per week; the circus now surrounds Van Persie. Is an aging Rooney who looks off the boil worth £300,000? That's the problem the club now have to deal with.
For a few years now fans of the club (and others) have stated that Manchester United lack a midfield. Paul Scholes retired at the end of last season and other than an aging Carrick, United were looking to start the campaign a midfielder down. You only need to look back to last season's game at Old Trafford against Manchester City where Giggs lined up in centre midfield. Fantastic player in his prime however when a 39-year old left winger is your central midfield option, what does that say about your central midfield? The club tried to rectify this with the signing of Fellaini however he's not been great. During the summer United fans said City overpaid for Fernandinho, I predicted that Manchester City would have the best partnership in midfield this year and United would be left looking envious. I still feel like this is the case. As for Cleverly, the less said about him the better. Cleverely had 3 assists and 2 goals out of 23 appearances during the last campaign, I did question if this would be the year where he finally loses the 'England prodigy' tag that Ferguson liked to pin to him. It seems like my prediction was right.
I appreciated I'm going into far too much detail now so I'll trim it down. I predicted Anderson was on borrowed time, Valencia gaining a reputation of a 'one trick pony' (knock it pas the defender and sprint).
I hope you're able to appreciate why this would be a mammoth task for any manager. Quite simply, the squad wasn't there.
For the record, @j0rd isn't an idiot.
One final note, apologies for any errors - I need a half time beverage, I am not checking over this post.