Manchester United knows better what they should focus on now and it is good they put in all their effort into what will give them the best result at this point. They should not waste their effort into what will not give them good result at this point in time now. The premier league can only be battled for not to be in the relegation zone but the Europa league is what is most important for them now. I trust Manchester United more in the Europa league than I trust them in the premier league.
Completely putting all their focus on the europa can actually put them at risk of relegation in the Premier League so I don't see that as the best reaction for them but rather trying to make a balance such that they will be able to secure a spot on the Premier League table that keeps them away from relegation and also try to win the Europa League title which could give them an automatic ticket to the champions league next season. Currently going by their performances it's very much achievable but they will need that extra effort to get it done and position them right for a better next season.