Surely, United management also considers how their performance is at the beginning of the season. But before that, we try to wait for how United performs in the summer transfer market. Amorim certainly hopes that his target for several players will be realized to compete next season. Only if that doesn't happen, of course, as you said, the possibility of dismissal could also occur.
I don’t think the Manchester United management board have any excuses to make this season they simply let the club down themselves, they failed to sack the manager early on as the season started, and when they got a new manager they fail to back him and seriously it was what affected them this season. I didn’t see the reason to why they brought in Amorim and without actually backing him in his first transfer window.
Manchester United this season not winning any trophies or even having any European competitions to participate in next season is good in my opinion because it will open the management eyes to the club depreciation and would probably do a very big squad overhaul this season