Ferguson struggled for four years. He took over a United side that (allegedly) had a terrible drinking culture within its ranks. I’ll let you guess which names spring to mind regarding that. In fact he was minutes away from the sack as United were losing to Nottingham Forest in the FA Cup in 1990 and got a late equaliser. From there United went on to win the cup beating THEM up the road. After that it was a trophy a season, almost, for Fergie and Man Utd. Love him or loathe him there is no doubt that he is the most successful manager in English football.
The other thing is that when Ferguson took over, Utd hadn't won a league title since 66/67. He came in in 1986 so that was 20 years with only 3 cup wins in that period (yes I know in 68 they won the European Cup). OGS has joined a club that is now used to success and the fans will demand it (and probably the media as well). He won't have time to build.
Always thought that Moyes was the sacrificial lamb as I doubt anyone would have wanted to immediately follow Ferguson but they have had no league success since and probably won't for some time!!