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.