I agree, SC really messed up when they left the ACC. They tried to get back in when the conference shake ups started but the ACC said no because they already had representation in South Carolina through Clemson. Clemson actually pushed to get Carolina back in the ACC from what I heard. But it wasn’t meant to be.
The story I read was when Carlen looked into rejoining, the ACC asked for too much money. A ridiculous amount for the time, but the regional TV package was more valuable than it is today. Until the middle 80s you could only be on one national broadcast per season, the Notre Dame rule.