United needed to rebuild, the squad was
and Moyes was bought in to oversee the transition, hence while they gave him a 6 year contract. Sacking him when he barely got any of his own players in, to keep it 100% was harsh. There was always going to be a drop off from Fergie, if no one didn't expect that, then they are idiots, Moyes was set up to fail, tbh.
On the appointment itself, Moyes being given a 6 year deal, without having won any silverware or CL football, prior to becoming manager was ridiculous. His away record vs Arsenal, United, Liverpool, Chelsea was horrid. You can blame Fergie partially for that as well, who pushed for Moyes. Aberdeen Fergie was shytting out trophies both domestic and international level, before he got the job, Moyes achievement was getting 4th once and a to a FA final. Avram Grant has a better resume then Moyes for the job.
And the 3 managers before Fergie all had at least 3 full seasons in the job. The worst was sacked just before his 4th full season. All longer than Moyes, LVG and Mourinho.
The board are to blame, for all that has gone on. When a big club has a dip/decline over a couple of seasons, it usually begins at the very top (just look at Arsenal, Milan as examples, if you want smaller examples, look at Villa and Newcastle under Lerner and Ashley, gone from established PL teams to jokes, because the owners didn't want to spend anymore). Starting with David Gill ducking out when Fergie did and leaving the out of depth Woodward to do everything without an experienced hand to guide him, which effectively phucked up the first year of transfers. Everyone but LVG knew he was getting sacked after the FA cup final. Hiring Mourinho after that Chelsea season, giving him an extension and then not backing him in the summer window.
Barring Real and Chelsea, swapping managers in and out all the time doesn't really bring success or stability to a team. And half of Chelsea success has been down to interim coaches. RDM, Rafa, Avram, Hiddink, all did equal or better than Jose did in Europe with majority of the same players.
If Zidane wasn't available, who else is there for United to get, if they give Mourinho the Spanish archer. Blanc? Maybe because of his United connection, who else is there? Everyone else is busy right now. It's all fine sacking but unless you have a prime candidate identified, do you want the same sort of situation that happened with Everton last season?
Mourinho was hired because Woodward needed to get the fans on side and let's not forget a portion of United fans wanted him in, to at least deliver a league title, which he had done at his previous 5 club jobs. It's not like Mourinho heel turn has come out of the blue, United fans knew what he was like and his supporters still wanted him and as far as I'm concerned they getting everything they deserved with him in charge. Like I said before, United fans are spoilt and don't know what real struggle is, like Citeh fans have had to endure. Their worse span in my lifetime of not winning anything is 5 years and that was from 85-90.