Conversation so far:
Where did Ruhollah Khomeini live before returning to Iran?
CANNOTANSWER.
What year did he return to Iran?
1 February 1979.
Why did he decide to return?
Khomeini was not allowed to return to Iran during the Shah's reign (as he had been in exile).

Question: Why was his exile lifted?
Self-contained rewrite: Why was Ruhollah Khomeini exile from Iran lifted?