The frustration was there before they started leading and is like the players are truly not playing to instructions given by him because I see no reason why he would be uncomfortable each time Manchester United have a game, before 10-15 minutes you see him feeling like he's on a hot seat, what is really wrong with him? Even when his side scores you can never find him celebrate like every other coach does and that impression shows that he knows his team won't hold on to that lead for long and it will happen that the opposition side will equalize in no time, like this man knows he can't trust his players completely.
When Bruno was to take the kick Amorim was looking elsewhere, mehn...this man has lost the confidence of a true coach. I agree with you, with the machines they have winning with luck is something that's not suppose to be happening, and if you check is just few players that has that courage to keep on playing for the club without being frustrated on the field of play and Benjamin Šeško is one of the frustrated players, like he's not having the best of days at the club.
I understand Amorim is under intense pressure, yet, he's not encouraging his players by allowing fear overwhelm him in the pitch. True, he doesn't celebrate, that's not ok. My pity goes to Sesko, he was better off where he came from, coming to Man U this season may not favor his momentum. The coach is slowing him down, by benching him, it's lowering the striker's morale, why then did he purchase him if he knows he wouldn't be featuring him at the start of every game.
Whenever a coach celebrate he feels happy with what his players have done and it will motivate them to keep pushing and showing some abilities that no one expect from them ,like the hard work will continue to show but when Amorim choose to sit and watch it will look like the players are not trying their best, as far as I'm concern, Manchester United need all the support they can get to keep doing what they need to do because if Amorim continue like this I don't see them having too much to offer. As for the player Benjamin Šeško, it will be frustrating and he can't do anything other than to endure because he choose to be in this club but I know the time will come when he'd get his regular start up.