I think Sir Alex was also part of the problems that befell Manchester United when he resigned. News then had it that he was the man that handpicked his successor which was David Moyes. That was the genesis of Manchester United problems, an inexperienced coach handling a team like Manchester United at that time, this was a title winning team that was handed over to him.
I totally agree with you on this, even in history, it mostly doesn't end well when an outgoing person handpicks his successor. I once read an article about Ferguson picking Moyes. How could he pick an inexperienced coach to manage a team like that. Moyes has been coaching Everton for almost a decade if not more and ends up mid table, how on earth did he think such a man was suitable for the Manchester United job back then! So I agree with you when you said Ferguson was part of the problem.
He was only tryna be good to his country brother little did he know that his kindness is gonna result to a destruction to the team he labored so hard to build, sir Alex Ferguson pick David moyes believing that he might deliver but David moyes failed and deep down I'm sure he's kinda sure sir Alex Ferguson has regretted it and we all have seen his efforts to repair the team, and in one way or the other the team bored is not helping matters too.