Leaving the ACC killed MBB, and made no significant difference in all other sports. Frank McGuire, as great a coach and personality that he was, carried a chip on his shoulder throughout his career, and it very much showed in Columbia.
To his credit, though, he complained about the ACC tournament both at UnCarolina and at USC. He had several job offers after leaving the Philadelphia Warriors. Why did he choose, in 1964, to return to a conference whose basketball policies he abhorred? I'm certain that many around the ACC wondered that too, and what was USC thinking hiring him. Nobody in the ACC would have begrudged our success per se, but McGuire had irritated too many officials around the league while at Chapel Hill. As I've stated on many occasions, USC was merely in the crossfire between McGuire and league officials. Remember, leaving the league was Dietzel's idea/folly. Frank merely had to go along, thinking/hoping that his program was on solid enough ground to succeed as an independent. It didn't take but a few years to discover that the ground was not solid.
Go back to the early '60s. Clemron was enjoying some success under Press Maravich (Pistol Pete's dad). Frank Howard (also Clemron AD) was about as unsupportive of hoops success as you can get. Press got no raise, and when Everett Case came calling from Raleigh to offer Press a position as his assistant at NCSU with a larger salary than Clemron was paying, well of course he jumped.
Interesting how Dietzel and Howard, both head FB coach and AD at their respective schools, did not like a non-football sport showing them up. Which is why, as I've posted before, it's a bad idea for the head coach of any sport to also be the AD at the school - potential conflict of interest.
Indeed, USC is in a much better position in the SEC than in the ACC. But that does not negate the unwise move to leave the ACC almost 50 years ago. An objective, impassioned person 50 years ago would have recognized the folly of secession. Over the years, some posters have justified leaving the ACC as the only way we would have joined the SEC. Not buying it. Look at Mizzou & aTm leaving the Big XII, and Maryland joining the B1G.
The BOT, with one notable exception, was suckered by Dietzel that things would be better as an independent.