I also agree, it is not fair to only say ETH is the cause of Manchester United's bankruptcy...
the problems are different, and are related to the determination to keep a coach who is not capable of managing a high level team.
i am not the type to say that you have to change a coach every month, but keeping an incompetent coach for so long has created a lot of problems, let's say, structural.
Even if you change coach it takes a while to fix things that by inertia continue to go wrong.