My quick calculations show that, in non-conf play, your opponents were, collectively, 82 games over .500 while theirs were 45 games over.
But, in conference play, your opponents were 118 games below .500 while they were only 16 games below.
I'm not sure is WIS includes your opponents' opponents in the SOS tally or not ( I think they do). But, regardless, your SOS is rightly worse.