I'm not sure if I get the logic of Notre Dame leaving the Big East for the ACC, unless it is driven by sports other than football and basketball. The Big East has been a basketball conference at its core, with the football part an ad-hoc venture that seemed secondary to the urban East Coast Catholic schools at the core of the conference. With the exception of Boston College, those Jesuit jump-shooters are still around, with folks like Marquette and DePaul added in later years.
The latest turmoil might have tipped the balance; with a lot of new southern schools like Houston and Central Florida filling the voids left by defections, the Big East will lose some cache and some ease of travel. Getting into to the ACC, where the basketball is on a par with the Big East and the other sports are better seems to be a help to the prestige of the non-revenue sports.
The funky addition to this is Notre Dame becoming essentially a half-member of the ACC in football, pledging to play 5 games against ACC foes. They're at 4 at present, with Pittsburgh and BC being regulars on the sked in the last decade already. As conferences get bigger and nine-game in-conference schedules becoming more common, it will be harder for Notre Dame to get good games in October and November as conference season kicks in.
This also gives the Irish an easy transition into the ACC if they opt to become a full member-going from 5 games to 8 or 9 would be a more-manageable shift.