One of the articles on the BBC Website 'asks' - "Where it went wrong for Man Utd manager".
I think the obvious answers are
1) the supporters expect too much too soon
2) the finances of the club are so precarious as to make anything other than constant success unviable
3) the is an unwillingness in modern top-flight football to allow a manager to develop and craft a team for long-term success.
Don't put all the blame on LvG; supporters and club officials alike need to accept at least as much blame. If they do appoint Mouriniho, I hope they end up in the bottom three next season, and lose many of their top players during the season. The same goes for Man. City.
On idea I heard the other day was for UEFA, at least, to require only players playing in a nation's home league to be eligible to play for that nation's international team - ie Gareth Bale would have to play for Spain, Aguerro for England, etc. .