Ten Hag is a wasteful coach. During his time in United was when United spent a lot of money and got no result despite the huge amount of money that they have invested in the club. De Gea was sent out of the club by Ten Hag and the management had too much believe in him to the point that they gave him total control on making decisions and buying players of his choice. That was what crumbled United financial strength.
Erik Ten Hag was responsible for the downfall of Manchester United till this present time. We know how did his best but it was not just good enough and watching him implementing inefficient strategies for the club, definitely mediocre for him and the club. He did also made some inappropriate signings for the club, bringing players he felt was good enough but only signing them out of favoritism.
Manchester United suffered severe losses and humiliation in games, and the club did healed from the wounds Erik Ten Hag inflicted on them and the new boss, Ruben Amorim have promised to strengthen the club to become a better version.