The October Revolution was built on the social issues that confronted Russia, the lack of any democratic processes in the Provisional Government, the poor conduct of the war and its social costs, and the radical and progressive agendas of much of the Russian working class and peasantry. This lead to the atrophy of support for the Provisional Government to the point that the Red Guards didn't even have to kill anyone to take over the White Palace, the growth in social and political power of the Petrograd Soviet, and the rise of the Bolsheviks and the SRs as the political mainstream of the nation.
If Lenin hadn't been a communist, the Provisional Government would probably still fall apart. Perhaps earlier (as in Hnau's "A Lenin-less World," where it collapses during a different July Days), or later (less likely, considering how weak it was by November 1917).
While without the Bolsheviks you are going to see a bit of a different relationship between the Petrograd Soviet and the Provisional Government, ultimately the Petrograd Soviet is full of radical, anti-war workers and the government is full of liberals who lead idiotic offensives.