Conversation so far:
who are released and armed in the Russian Revolution events of september 1917?
The Bolsheviks were released and armed in the Russian Revolution events of September 1917
who freed the Bolsheviks in the Russian Revolution events of September 1917?
Petrograd Soviet

Question: why were the Bolsheviks freed?
Self-contained rewrite: why were the Bolsheviks freed in the Russian Revolution events of September 1917?