When you hear of a major corporate bankruptcy, always trace back to the investment banker or 'private equity' firm that loaded it up with debt and sucked it dry. You'll almost always find one 5 - 15 years back.
How did they go bankrupt? The usual way - investment bankers / private equity got their claws in them and sucked them dry. In this case it was Cerberus.
That’s what ole honorable Mitt Romney did in his early days with Baine Capital.