It doesn't seem appropriate to compare countries and clubs. But you have to know Rangnik led Austria to a 3-0 win over Croatia. Remember this is Rangnick's first debut. So if you look at this of course I'm sure here is not Rangnick who makes Man United bad, but I think there are mental and motivational problems from the Man United players. That's what Rangnick hasn't been able to overcome at Man United. So at the moment Ten Hag's decision to sell some players and let them go is the best move for Man United's progress. But I'm also not sure next season Man United will be good and stable.
Rangnick did not have much time to prove his worth at Manchester United as a coach. I don't know which players he brought to Manchester United during his time in charge. But I can think of something different about Ten Hag, he has more trust from the Manchester United management to buy some players and sell others. Do you realize it?
Apart from not having a lot of time Rangnick is also required to restore a team that has fallen and this is clearly quite difficult to re-establish trust like this and is tantamount to making something that has been broken into one whole again.
It would be very difficult even if he could and it was true that his time was also limited. On the other hand, it's not only the coach who has a problem, but the players and management also have the same role and this season, MU has been very chaotic in many ways.