I remember taking a beating on this forum when I said I was glad Lovie Smith was gone. Buccaneer's fans seemed all to glad to have him. Now they're seeing what we saw: Lovie Smith was not head coach material. He was in fact, a hell of a defensive/special teams coach as you pointed out and he was the architect of the St. Louis Ram's defense the year they went to the SuperBowl.
The Bears mistake with head coaches time and time again has been to focus on "Defensive" minded coaches. Trestman was supposed to be a 'break' from that and by the performance of the offense last year (Total yards, points scored, etc..) it seemed the Offense was "fixed" but the Defense was in fact broken (and old.)
What we saw this year was IMO the culmination of several factors, including the fact that Lovie Smith did leave the team "old" and "bare" and that Trestman wasn't the Offensive minded coach he appeared to be last year.
As much as Mel Tucker never did a thing to adjust the defense or swich things up, neither did Trestman this year. According to some of the commentary I heard today on Sports Radio, the lack of Trestman "adjusting" the Offense and his inability to deal with Tucker's horrible offense was ultimately his undoing this year.
As one station reported it, the decision to clear out the Front Office and Coaching staff was made 2-3 games ago.
Yet another house cleaning for Bears fans. I was hoping that Harbaugh might come to Chicago. No such luck.