It's not an easy thing to restore United's glory like the Fergie era, many great coaches have tried so far, moyes, van gaal, solkaejer and even mourinho has certainly failed to repeat what fergie had done so far, I think some of the coaches mentioned above are a coach who has a lot of experience and has won trophies during their coaching career compared to Ten Hag who I think is only a local coach, even though he managed to bring ajax to develop quite well in the eradivisie league, to be honest, managing United is not an easy thing to do, So United fans don't expect too much if they don't want to experience a bigger disappointment later.
The biggest issue will no doubt be that if as expected the new manager gives the squad a huge overhaul, and brings in a lot of big name players for big money, then the board and the fans will want to see an
immediate improvement in results. But of course if you are completely overhauling a team, it takes time for the new players to bed in, it takes time for everyone to gel together and start playing as a team instead of a bunch of individuals... and results can suffer until this happens. The biggest failure in modern football, particularly at the top level, is that managers are not given enough time for their changes to take effect. Clubs never seem to learn.
Honestly, it is hard for any manager when he has a team full of superstars and still the team is not performing. A lot of questions are generally asked in certain situations and often there is not much answer to those questions. a Coach needs to be someone who will have authority over the players. And a coach is also someone who should be able to encourage the players to give their 100% on the field. A coach is a teacher and also a friend, I hope this coach will be given enough time by Manchester United and also will be able to show some improvement with Manchester United.