"Notre Dame reportedly makes around $9 million per year from NBC, which was a level that made it the top TV revenue school back in 1999. In contrast, ESPN’s Outside the Lines reported last week that the Big Ten is currently making $242 million per year in TV revenue which is split equally among the 11 schools, meaning that everyone from Michigan to Northwestern is taking in $22 million per year. Think about that for a second: the vaunted Notre Dame was the #1 TV revenue maker in the entire country up until just a few years ago, yet it’s now only #3 in its own home state behind Purdue and Indiana (and less than half as much of each, at that)."
It's not about money with ND. They'd make piles of money MORE in the B1G. It's about independence to them.