The football agreement was a concession by Notre Dame. What it wanted was to be in the premier basketball conference, and other Olympic sports. ND agreed to invigorate thyACC football teams by agreeing to a rotating 3 game season. ND football adds seats in stadiums, TV exposure, and SOS.
You forget, in the modern era (post Boomer)except for FSU,MIAMI, and Clemson you'd be hard pressed to find a national champion in the ACC. Maybe I recall Virginia.