I won't be surprised that with this trophy that Amorim was able to give the club it would be a start of something great. I'm willing to even him(Amorim) the benefit of a doubt that he the reason he wasn't able to do well last season was because of the short period of time he was given and that this incoming one would be a great one for the club and fans as well. Who knows, he may be able to restore Man UTD to the form that Sir Alex Ferguson left them, it's only a matter of time and patience though.
If you mean that the cause of Manchester United's poor performance in the previous season was due to the limited time Amorim had, I personally don't really agree with that. Because basically if it's true, time was a barrier for Amorim in the previous season, why until the end of the season Manchester United's performance was still bad. Because supposedly, if time is the reason, Manchester United should be able to perform well in the middle of the season in the English league. Because Amorim at that time had certainly adapted to the style of play that suited the Manchester United players and he also must have found a good strategy at that time. But the reality is that Manchester United's performance remains poor and there is no development. Therefore, I personally do not really agree with your assumption.
But even so, I also won't be too pessimistic about Amorim at this time. Because before I see Manchester United play in the next season, I will not be too pessimistic about Amorim. But if for example Amorim can't make Manchester United's rise from its slump, I don't think he deserves to be the coach of Manchester United and most likely he will be fired by the management of Manchester United.