When has ND ever lost any sleep over Fredo. ND doesn't care about Fredo. They weren't founded by or run by the same order of the Catholic church.
Fredo doesn't help or hinder ND joining or not joining the ACC or any other conference for that matter.
ND is interested in 1) keeping it's football independent. 2) Having a very good to great home for all of it's other sports. That's why ND left the BE. As the BE is presently constituted, basketball would have been fine. However, it's going to be a crap conference for Olympic sports. ND takes Olympic sports seriously.