Conversation so far:
What did John C.
Frémont get courtmartialed?
Fremont was convicted of mutiny, disobedience of a superior officer and military misconduct.
Did he resign after this?
CANNOTANSWER.
Why did he end up resigning?
Polk felt that Fremont was guilty of disobeying orders and misconduct, but he did not believe Fremont was guilty of mutiny.

Question: What did he do after he left the military?
Self-contained rewrite: What did Frémont do after he left the military?