The problem these days has to do with clubs/fans wanting instantaneous result. Klopp's Liverpool didn't get where they are over a fortnight, it took time and should Klopp leave today, I doubt Liverpool would have much to worry about over the next three seasons. Man Utd needs to get a coach in whose ability and football philosophy they believe in, then, entrust him with the WHOLE process. but that has seemed to be too much for the club
Thats the game for you this days, even the smaller teams sack their managers after few bad games, and you wonder what they expected the manager to do with the players at his disposal. Liverpool's case is kinda different as klopp has been able to get the team playing the way he wants then to, he is able to elicit great performances from them.
United do not have to stay so long away from the "top" to get back the quality performances they were known for in the past, their players do not just seen to have the desire or the traditional united flair to perform at the top of their game, they need a manager that'll spur their players on to perform, just look at what pep is doing at City as a perfect example.