I have a vague idea of what criteria the selection committee uses to determine what teams get into the dance at best. What I do know is that Notre Dame got a 6 seed, which means they were very, very comfortably in, and Illinois did not get in. Notre Dame must have a much better resume than Illinois then, right?
Notre Dame was 23-11, with 5 wins against the Colley Matrix top 50, but 6 wins against teams ranked #235 or lower. 3 of their losses were to teams ranked #28 or higher, but another 3 were to teams that finished #80 or lower.
Illinois was 19-14, with 5 wins against the Colley Matrix top 50, but only 3 were against teams ranked #235 or lower. 8 of their losses were to teams ranked #28 or higher, but another 4 were to teams that finished #80 or lower.
So removing completely understandable losses (#28 or higher) and complete garbage wins (#235 or lower) changes things a bit. Notre Dame is now 17-8 with 5 quality wins and 3 bad losses. Illinois is now 16-6 with 5 quality wins and 4 bad losses.
I'm not here to tell you which resume is better. I'm not trying to say that ND didn't deserve in or that Illinois did. I'm sure that if different arbritrary cutoff points were used in the Colley Matrix (or any other rankings) this could tell a different story. What I am trying to say is that a reasonable person could look at objective, reasonable, unbiased, wins-and-losses data and think Illinois had every bit the season Notre Dame did, if not better.
One is a 6 seed; one is not in.