Manchester United is scared if they might enter relegation zone if the manager is still Amorim, but they forget that they signed Amorim because Amorim was successful with Sporting Lisbon.
Amorin was successful at Sporting Lisbon but will not guarantee it at Man United --- the management may think of sacking Amorin if he continues to fail in every match, but don't forget that sacking costs money again. 
Emery once trained Arsenal, but he was not successful. Manchester United better to recruit Xabi Alonso, Ancelotti or Pep, we haven't see star managers manage Manchester United.
These 3 coaches will probably not want to handle the Man United club. LolBetter to give Amorin a free hand, and give him fresh funds to overhaul the squad to buy players and discard bad players.