Actually it was indeed a sabotage. IIRC there was a provision in the Braves' lease of War Memorial Auditorium that if the season ticket sales dropped below a certain amount (5,000 I believe) then the team could get out of the lease. As others have mentioned, the team was really good in the 1974/75 and 1975/76 seasons. With McAdoo a pending free agent, he was traded to the NY Knicks midway thru the 1976/77 season for a stiff, John Gianelli, and cash.
The Braves became a losing team, attendance (including season tickets) dropped and they were able to get out of their lease.