5. Poor decisions
The last reason is the poor decisions made by Moyes.
The biggest mistake - something which might be haunting the Man United manager - would be rejecting Sir Alex Ferguson's advice to keep his backroom staff.
The Scot brought in Steve Round, Phil Neville, Jimmy Lumsden and Chris Woods from his former club Everton as he shipped out Ferguson's favourites Mike Phelan, Rene Meulensteen and Eric Steele.
If Moyes had retained the coaches, he might have had a better start to the campaign as all of them knew the club.