He just didn't become a player that Erik Ten Hag didn't like, which is why he was discarded after his long service. Because if we look at Erik Ten Hag, he chooses players based on what he likes, the proof is that he brings many players from his former team, and those are the players he likes.
De Gea did make some mistakes at Mamchester United, but we must judge as a whole, because Manchester United's defense is also problematic, making goalkeepers difficult.
Onana even I see worse than De Gea, maybe we have seen a lot of mistakes he made during Manchester United's recruitment this season. It doesn't look special at all, even though he is one of the players who performed brilliantly at the World Cup.
It is important to note why Ten Hag is more interested in bringing in some of the players he previously managed with his previous club. also, not because of Ten Hag's liking for the players he has coached. but more precisely, the players he brought in, especially those who had worked with him before, knew very well what the coach wanted. apart from the player having quite good talent and quality, Ten Hag wants to implement his system at Manchester United. we know very well that Onana is one of those who has been under Ten Hag's guidance while with another club and it is hoped that this goalkeeper can meet Ten Hag's expectations. unfortunately, Onana has not been able to do her job as fully as possible. He made several blunders that he shouldn't have made, that's why his performance wasn't good. even though if we try to look at every statistic in every match, Onana isn't that bad. although in fact, as I said, Onana made several blunders. apart from that, Manchester United's defense is poor.
As for De Gea, the goalkeeper has become an iconic player with The Red Devil. unfortunately, the system that the United coach wants to build is not suitable for De Gea. that doesn't mean De Gea can't play well again, it's just that Ten Hag wants to implement a system that involves the goalkeeper taking part in building attacks. that's why Onana was the main choice at that time, with limited financial conditions for shopping. It's a shame that United is experiencing a lot of problems within the United camp, I don't think the team's performance as a whole is stable. so, it's only natural that there will be an impact and influence.