Why was industrialization more difficult for russia despite its large population?

The large Russian population in the 19th century remained primarily rural, not moving to cities.  Most of the rural population were former serfs who continued to work at agriculture in old world ways.

Between 1850 and 1900, Russia's population doubled but remained mainly rural.  And that rural population operated mostly in small, peasant farm fashion.  There wasn't the same acceleration toward urbanization seen in nations that were industrializing more rapidly.  Russia's autocratic government under the tsars was also not ready for the sort of progress needed for industrialization.