Fans in general do not care that he is there trying and trying to fix everything - they care about the result, and with the arrival of Amorim in the club you can say nothing has changed and the team continues to lose and keep on low positions in the league table. Outside of the championship they seem to have everything more or less, but inside - terrible
Nothing has changed for United because even though Amorim came in and changed things for the better, in the end it still failed.
In the Premier League itself United are like a mid-table club and it's quite easy to beat them at home.
The fans will never care if he leaves or not because United are so far behind the competition and they are having their worst season probably at the moment.
The only impressive thing in the Europa League is that they are unbeaten so far but no one knows what will happen to United in the last 16.