What are the main factors for the Bolshevik's victory in Oct 1917?

Answer 1

The Bolsheviks' victory?

http://www.spartacus.schoolnet.co.uk/RUSnovemberR.htm

... and others:
http://www.google.com/search?hl=en&as_q=why+bolsheviks+won+1917&as_epq=&as_oq=&as_eq=&num=10&lr=&as_filetype=&ft=i&as_sitesearch=&as_qdr=all&as_rights=&as_occt=any&cr=&as_nlo=&as_nhi=&safe=images

Answer 2

That first link is well done. The war had exacted a great toll on the Army, the economy was in shambles, and the army was in disarray, and angry. The Bolsheviks just happened to be there, and organized.