What Ruben Amorim did was very appropriate because he certainly had analyzed the factors why Manchester United often failed to be consistent every season. Maybe some people will consider Amorim a little selfish for his decision not to involve Ruud van Nistelrooy and a number of staff, but if seen from the positive side Amorim has started a good decision and wants to maximize this opportunity purely under his system.
I also think that what Ruben Amorim did was not wrong at all because apart from wanting to maximize the performance of the Manchester United team itself purely through his own guidance, he probably did not want to be considered as someone who still depended on the old coaching staff when he coached the Manchester United team. So what he decided was actually the result of his own thinking because he had more confidence to make better changes with his own staff at Manchester United.
Is Ruben Amorim a little insecure if Ruud still handles the team or works with him? Is he also afraid that the fans will praise Ruud more than him because before he coached the club Ruud was first the interim manager. I think Ruben Amorim just doesn't want to be involved with Ruud in his coaching system, meaning he is ready to accept all the risks he will bear and the fans have placed high hopes on Amorim for the rest of this season.