You know little about money if you think £4bn profit on something that should be earning you in the tens of billions in your lifetime if you managed it correctly is not miss management.
You can still turn a profit and miss manage
We're all in agreement that Glazers have been poor stewards that will nevertheless receive a king's bounty in reward of very little they actually did except sitting on an asset that kept appreciating because of the torrent of cash flowing football.
Yes they maybe could have profited
even more if they ran the club differently and better but well, that requires effort and a long view.
Though in reality that's actually debatable. There's a reason "sportswashing" or "financial doping" as we call it now is so potent at breeding success in sport. It's a lot easier to maintain your competitive edge when you don't care about being sustainable or profitable. Always has been in football.
I believe Berlusconi actually did lose a fair bit on AC Milan, all told. Selling it mostly wiped the bulk of losses. Now of course he reaped many indirect benefits in clout, influence, prestige or for his other businesses. But the club itself was just bleeding money in operational terms, at least officially.
Probably the same for Tapie in Marseille. Louis-Dreyfus in... Marseille. And most of the millionaires that did it partly for the love of the game.
That's why they all want a closed league : That's the only way to keep that insane gravy train rolling. Otherwise it's down to TV rights ever increasing (not guaranteed) or Saudi Arabia -or another- pumping more billions in the system.