Manchester United actually didn't have a bad performance. They were very effective offensively throughout the match, but if there is a problem with something, it could be Casemiro's penalty and the red card he received. Everything in Galatasaray's favor became more evident after that red card. Before that, Galatasaray, which scored 2 goals with 2 counter attacks, found strong positions against ManU, which was missing. As a result, they scored the third goal and won the match. ETH may now need to be questioned in Manchester United.
In terms of play, Manchester United were indeed able to perform well and create dangerous attacks, but the carelessness of their own players made everything fall apart. Casemiro's red card gave Galatasaray more freedom, but Onana's poor performance was also the main cause of the defeat. Erik Ten Hag is really quite confused about the problems plaguing his team. I think Ten Hag must have the courage to make decisions for players who cannot make a big contribution to the team. Now Erik Ten Hag's fate is truly on the brink.
Casemiro's red card happened because Onana made a mistake when he passed to him under pressure, while it was clear that Mertens was pressing him and when it became clear that Mertens was likely to score, Casemiro basically had no other option but to foul. So if it wasn't for Onana, Casemiro wouldn't have gotten a red card. It was lucky that Icardi didn't score a penalty right away, but then because of the Manchester City defender's mistake he still managed to bring Galatasaray the victory.
Not very clear In the last round of the Champions League Manchester missed 4 goals, now only 3, so there is progress here).
Otherwise everything is bad, Onana is nervous and he should be removed, the defense understands that the goalkeeper can make mistakes and also plays unreliable, in the attack is a crisis and given the spending on transfers under 500 million euros, Ten Hag needs to quickly show results, otherwise it is unclear why they keep him.