In the Europa League Manchester United has improved slightly after Amorim became their coach but there are still many changes that need to be made because so far Manchester United's performance has not been stable. Amorim's motivation may be very high in the Europa League because in almost all competitions they have lost the opportunity to achieve a trophy so that only the Europa League is the only hope they can realize when they are able to play much better in the future.
Another challenge is only in this competition the opportunity for Manchester United to qualify for the Champions League by winning the Europa League and will give them one ticket to qualify for the Champions League. The tight competition in the Premier League makes it difficult for them to break into the top four, making it difficult for them to catch up with the points collected by several teams in the top five.
It makes sense as you said. Amorim's motivation is currently only focused on the European league, because by focusing on the European league, besides getting trophies, they can also enter the UCL league next season. Isn't this season Man United entered the European league because they managed to win the FA Cup trophy so they automatically entered the European league. Maybe this is what is on Amorim's mind right now, focusing on the European league might be much better than the EPL league, especially since Man United's performance in the European league is still good, they have not lost in 6 matches and are currently ranked 7th in the European league standings.
Coach Amorim is actually a great coach, what happened to Man United is not entirely Amorim's fault. He just needs a process and support if there is criticism, it should be constructive criticism. Just look at Liverpool, why is it getting better even though the coach is new, because at the beginning Liverpool was good when coached by the previous coach, so when the new coach came, Liverpool was still good. It's a different story with Man United, since Sir Alex left, Man United has often changed coaches, as a result Man United has become chaotic. So how can Man United be like before? We must be patient and give support to Amorim.