But I didn't say that it didn't make a difference, did I?
Margin of victory matters to the computer rankings. The computer rankings determine how the selection committee views your opponents. The committee makes its selection based on how you did against your opponents. But the committee doesn't select teams strictly based on the rankings. So some teams with good NETs get left out because they have bad resumes.
As it said above,
Not nothing, but not very important
NET and other computer rankings
I didn't make that up. That's the committee's explanation.