I was a little surprised by the management's dissatisfaction with Ruud van Nistelrooy to handle Manchester United that he seemed able to bring Manchester United to its best performance, because we know that Ruud van Nistelrooy knows more about what Manchester United wants, honestly I doubt Ruben Amorim and I also don't know anything that Ruben Amorim has done as a coach and the achievements that have been obtained I don't know, but it all comes back to the decision of Manchester United management in developing and making significant changes this season.
Amorim would not want someone like Ruud at the club, for a few reasons, Ruud is very close with the players and the relationships he has is threatening to Amorim. Ruben needs their loyalty, he's a "coach for the players", and handles the press very well when it comes to criticism towards the players. Imo, it's a blessing Ruud isn't at the club anymore, albeit he was doing a fine job (He showed qualities that ETH lacked in his approach for e.g. he wasn't stubborn at all, something ETH was famous for at United.) but Amorim will probably be more successful without him there and having his own coaching staff that he's brought in from Sporting.
Personally, I must give props to INEOS for how they've handled things this season, they've been ruthless and concise.
Amorim's achievements, similarly to ETH, are mainly domestic. However, both City and Liverpool had their targets set on Amorim and I think that says a lot.