Conversation so far:
What did John C. Frémont get courtmartialed?
Frémont was found innocent of mutiny, but was convicted on January 31, 1848 of disobedience toward a superior officer and military misconduct.
Did John C. Frémont resign after being courtmartialed?
President James K. Polk quickly commuted Frémont's sentence of dishonorable discharge and reinstated him into the Army, due to his war services.

Question: Why did he end up resigning?
Self-contained rewrite: Why did John C. Frémont end up resigning from the military?