What Erik ten Hag did was indeed quite appropriate for player discipline, but we also have to see that while Erik ten Hag was coaching Manchester United and at Ajax previously he had a lot of problems as a coach with players, not just with Jadon Sancho, I don't mean to defend Sancho, but I think Tenh Hag also has to lower his ego and prioritize the development of the team he handles.
I think Erik Ten Hag doesn't need to lower his ego. Because ego is necessary for a coach to manage his players. Just think about talented coaches like Sir Alex Ferguson, Mourinho, Antonio Conte, or Jurgen Klopp... what were their egos like? I believe what Ten Hag needs right now is to adjust his ego and personality to be more suitable, so that other players on the team don't lose confidence and believe that he's not favoring anyone on the team. With that, Ten Hag can slowly revive Manchester United.