are the words that explain Joe Gibbs being so low on the list, Sean Payton so high, etc.  Coughlin keeps getting rewarded for the Giants being in the playoffs two years in a row, which would be enough for a higher ranking, but his sideline hysteria, the internal squabbling, and lack of on field discipline, and his players' dislike of him takes him down.  22nd seems about right.  
One important measure of a head coach is the type of assistants he hires.  Using this standard, Jim Lee Howell belongs at the top of the heap historically, having hired Lombardi, Landry, and (I think)Sherman.  Remember, in his first few years Sherman was considered a genius, having brought in Tittle and Shofner to supercharge the offense.  The fans demanded his departure not so much because of the team's subsequent decline, but because he traded Sam Huff, who they worshipped.