The answer is simple - it's muttdoc's fault. It usually is. :D
I'll bet there was one team in your division that you didn't match up well with, for whatever reason. You lost 15 of 24 mostly tight games to one divisional team because of the matchup, but beat up on everyone else - about 18-6 with big run diff versus the 2 schlepps in the central. That's what happened to me when my 93 win team finished third in the division.