Sorry if I’m stereotyping.
My education essentially taught me that the serfs weren’t natural left wing allies and were actually very conservative, often being highly traditional followers of the Russian Orthodox Church and strongly supporting the Tsar and even being angry and rioting when serfdom ended.
Then we get Communism and the idea that religion is the opiate of the masses, persecution of all religions and far-left, socialist, revolutionary ideologies. What the heck happened in between? Even with humiliating defeats for the Tsar like the Russo-Japanese War, I can’t understand what changed the minds of such a conservative people and what broke an unbroken tradition of belief in a Russian Orthodox Jesus, Tsardom and Empire?
How did a party of workers and peasants even get popular outside of academic circles?
You’ve got the Tsar and aristocracy who wouldn’t obviously benefit, you’ve got religious minorities like Jews and Muslims who wouldn’t benefit, the Russian Orthodox Church wouldn’t benefit, the bourgeois middle class wouldn’t benefit and the working class outside of the cities seem to be very conservative.
I know that many mothers bravely protested the Tsar but that’s quite different to saying I am now a Marxist, I don’t believe in any religious rights and I want a revolutionary socio economic system run by Lenin and his friends. So where is the revolutionary support base really coming from? I don’t get it!
This is such a good question and I'm sure my answer will barely scratch the surface, but...
I think it's helpful to think about what constitutes a 'revolutionary idea' in 1917. Because while Marxism was alien to many ordinary Russians, Lenin's radical political messages were often familiar and welcome. 'Peace, bread, land!" This was Lenin's slogan throughout 1917, and it chimed with what many Russians wanted.
'Peace!' Russia did not fare well in the First World War. Discipline in the Russian army had completely broken down by 1916. Soldiers regularly deserted or mutinied. After the February Revolution of 1917, the Provisional Government made the disastrous decision to continue fighting when many in Russia were desperate for the war to end. Particularly because it was pushing up the price of food...
'Bread!' Prices were spiralling in Russia. Obviously, in this situation wealthy people were sheltered from the worst while poorer people suffered. Lenin could make the case that the Bolshevik Party, by ending the war and taking command of the economy, would see a fairer distribution of commodities like food.
'Land!' Many Russian peasants loathed their landlords. Indeed, since the late-nineteenth-century the countryside was in uproar as peasants turned on and attacked local landowners. Many peasants believed that they had an ancestral right to the land they worked, and that this had been stolen from them by their landlord. So, Lenin's promise of 'land' chimed with what peasants wanted.
We could describe these ideas collectively as a kind of 'folk radicalism'. Discontent with the Tsars and then the Provisional Government (PG) combined with this folk radicalism to give Lenin enough of a revolutionary support base to overthrow the PG and win the Russian Civil War.
Your questions about religion are crucial at this point. Because while many Russians might have subscribed to some anti-clericalism (according to which they thought that their local priest was corrupt, or a drunkard etc.), they were mostly deeply religious. Therefore, a very obvious gap emerges between many Russian people and the Bolshevik party.
However, the Bolshevik Party had time on its side. After the Civil War, once they controlled the media and education system, it was easier to raise the next generation as good, Marxist atheists. Still, Orlando Figes, in The Whisperers, writes about how even as late as the 50s, many Russian grandmothers would still keep religious tokens and shrines hidden away to pray to.