Conversation so far:
Why did Superstar Billy Graham return to the WWWF?
an agreement with promoter Vincent J.
McMahon (Senior.
What was his agreement with McMahon?
CANNOTANSWER.
How did people respond to his return?
CANNOTANSWER.
What else happened during 1977-1981?
Graham defeated Bruno Sammartino for the WWWF Heavyweight Championship on April 30, 1977.
Did he defeat anyone else?
Graham defeated Bruno.

Question: What happened after he defeated Bruno?
Self-contained rewrite: What happened after Superstar Billy Graham defeated Bruno?