I don't really doubt them, but sometimes I think that the relationship between players and coaches also has an influence. I don't know exactly what wouldn't work internally, but the board is not on the pitch playing, the board can be very bad, but the players and the coach can make the Difference on the pitch. The case of Chelsea is one that intrigues me because of what is happening, because Chelsea has players and has had very good players, it is almost the same thing that happens in the MU, and if you look closely, the quality of each of the players is very high. I am sure that if they were managed by an Ancelotti, a Pep Guardiola, even a Mourinho , the results would be different for both Chelsea and the MU. In the same way, the teams that I would like to see in the top 4 would be Chelsea and the MU.
Yes you are right that relationship between players and coaches is very important for team success. People in charge like board and management are important too but it is players and coaches who actually play games and decide who wins or loses. Chelsea is good example of this. They have a lot of talented players but they have not been doing well. I also think great coach like Ancelotti Guardiola or Mourinho could make big difference for Chelsea and Manchester United. It is interesting to think about how these teams would do with different coaches. I hope they can improve and compete at high level. Way players coaches and management work together is complicated but it ia clear that everything needs to come together for team to be its best.