Mangini was the last head coach we had where the buck clearly stopped on his desk. Part of the reason he got fired was that he lost some focus in 2007 with all the Mangenius crap and didn't completely recover in 2008. However in retrospect it is clear that you don't give your HC a 40+ QB and then hold him accountable when the guy gets hurt in the middle of the season. That was just bad news even if Mangini wanted Favre for '08.
Yeah and also expect Mangini to forcefully sit Favre, the legend, down at the end of the year because he's hurting the team by playing with his injury. Wasn't Mangini younger than Favre at the time too? That trade wreaked of not having Mangini's approval. Favre was dying to go to Minnesota the minute they drafted Aaron Rodgers.
Early in the process Mangini was opposed. When he realized that ownership and Tannebaum really wanted to make it happen he flopped over to the pro side because the easiest way to get fired in the NFL is to be the lone voice in dissension. Strong consensus organizations, like the Steelers and the Ravens, value the guys willing to stand up and argue against a move everybody else wants. That's because it increase the chances the team avoids bubble-think mentality which can be a weakness at times.