The scenario imagined not only by the right but by some on the left starts with a good-enough society. There are real problems, some of them quite serious, but on the whole most people are working, eating, having fun, raising families, not rioting in the streets. But the socialists condemn this society as profoundly immoral. So they recruit a few hundred people, and get some guns. They storm the capital, arrest and imprison (or worse) the government, and install themselves as the new government. They then impose a more moral society on the recalcitrant population. Which, of course, completely fails, making society worse off than it was before.
The paradigmatic "real-world" narrative is, of course, the Russian Revolution. Russia has some real problems, some of them quite serious: notably, they are doing quite poorly in WW I under the Kerensky government. However, they are a functioning society. Lenin, however, after being infected by the Marxist brain worm, decides that he cannot tolerate the immorality of Russia's burgeoning capitalism. He assembles and arms a few hundred Bolsheviks, arrests the Kerensky government, and imposes Communism on the recalcitrant Russian people. A successful defense against a Western invasion, conquering an empire starting with only wood for fuel, becoming a nuclear power, developing a somewhat successful space program notwithstanding, Russia under Lenin and his successors starts off a complete failure and only deteriorates from there, proving that anything other than
laissez-faire capitalism can do nothing but doom society to poverty and misery.
For those of you who unable to detect the creeping sarcasm, the above is complete and total bullshit. The first paragraph does not represent how any social change, much less a social change to socialism, actually happens. The second paragraph is not at all how the Russian Revolution happened.
There's another scenario: human society is making progress. Not any old progress (which is just the trivially true change over time), but a certain kind of progress. Our society today is
better than it was 100 years ago, and that society was better than it was 500 years ago, which was it was a 1000 years ago, and so on. The progress has not been linear of course; there have been interregna and backsliding, but overall society has been progressing. We are not yet at an ideal society, but we are closer than we were. And progress towards an ideal society might be asymptotic, but we should be closer still in another century.
This scenario too is bullshit, albeit more subtle bullshit. There's no objective way to evaluate any society. Most of us like our own society because it's the society we were indoctrinated as children to like. And, of course, those of us with privilege like our society because we have privilege; therefore, we believe we
deserve privilege, and it would be an injustice to lose that privilege to those less deserving. We see our society as closer to the ideal than any other kind of society just because it is what we actually have, not because it actually is closer to some mythic ideal.
Historical Materialism
Marx himself believed his great contribution to the world of ideas was not class struggle (Smith and Ricardo precede him) but the idea of historical materialism, which hardly anyone really understands or takes seriously. I take historical materialism seriously. I'm not sure I myself understand it, but I will share my thoughts anyway.
The "materialism" part means that human beings are constantly faced with material (concrete, real-world) problems presented by the environment Which berries are good to eat, and which will cause sickness or death? How can I kill this beast and eat its tasty flesh? What do we do about that asshole who hogs all the good food?
The "historical" part means that we reproduce these solutions in consecutive generations. Our children don't have to think too hard about the solutions their parents came up with, at least the solutions that work well enough. One specific part of these historical solutions are patterns of social relations. Hunter gatherers get used to one pattern of relating to each other, pastoral, horticultural, agricultural, and industrial societies get used to their own specific patterns.
Marx argues* that the material problems of the production (as well as distribution and consumption) of material stuff are of if not exclusive then at least primary importance and these problems "determine" (or at least strongly constrain) historically transmitted social relations. In other words, the means of production determine the social relations of production.
*Marx might not really argue what I say he argues. I put the arguments in his mouth not only to lend them additional authority but also because I present my understanding of Marx's arguments with considerable and possibly undeserved charity.
We have heritable variation and natural selection, so we expect that the "determinism" is in some sense evolutionary. Specifically, patterns of social relations that have relatively better (more or better distributed) material production will have a selective advantage over patterns with relative worse production.
Marx argues that "materialism" means that big changes in the means of production
cause big changes in the patterns of social relations
rather than the opposite. Marx further argues "historical" means that the the specific character of the pattern of social relations obtaining at any specific time and place as the means of production are undergoing a big change there
cause the specific pattern of changes to the social relations of production in response to the changes in the means of production.
(Please remember social scientists look at causality very differently from physical scientists: societies have orders of magnitudes more moving parts than even the most complex engineering projects. I will try to be more precise in more detailed explanations, but for here, causality in the weak sociological sense, as opposed to the the physical or even economic sense, is sufficient.)
Although this basic description is good enough for now, we can improve this theory considerably (notably that social relations can also cause changes to the means of production, hence the alternative label of
dialectical materialism). I will also discuss some good and bad criticisms of historical materialism elsewhere. Here, I want here to discuss some implications of Marx's theory assuming he's really on to something worthwhile.
One implication is the denial of idealistic progression as mentioned above. We do not, we
cannot, improve society by coming up with radically new and better patterns of social relations. Instead, we change our patterns of social relations in response to changes in the means of production. Briefly, Adam Smith and capitalism did not cause industrialization; industrialization in the specific historical context of late 18th and 19th century Europe, especially Great Britain, caused capitalism and Adam Smith. Similarly, if we end up with something like "socialism", it will not be because we imposed a socialist pattern of social relations on a more-or-less working capitalist society, but because capitalist society has itself created the conditions for revolution.
Revolution
Revolutions happen because of the specific way we create social systems. Human beings rarely think everything through from first principles: that's a prohibitively cognitively expensive way to solve most problems. Instead, we "reason" by habit, analogy, and tradition. If the means of production are relatively stable, then social relations will stabilize and reach a local maximum of productive efficiency. However, when big changes to the means of production happen (whether exogenously or endogenously), the regime of social relations of production are adapted to the old means of production. We retain this old regime out of habit and tradition.
Marx argues that new patterns social relations better adapted to the new means of production emerge within the old pattern. Because social relations generally entail power differentials, those with more power under the old regime are loathe to change it, protecting their power with even the most frightful violence. But because the new regime is more economically efficient, it has a real opportunity to successfully overthrow the old, but usually only after violent struggle.
Coda: The Bolshevik Revolution
In Russia in 1917, the Tsar lost legitimacy and abdicated, Kerensky's bourgeois "democratic republic" lost legitimacy, and everyone else, including the soviets, lacked the power or will to form a government. The Bolsheviks were not just a few (or even a few hundred) people: they had influence and popularity across Russia. Once literally everyone who might have had more power bowed out, only the Bolsheviks had sufficient legitimacy to form a government. So they did. And then they started solving Russia's considerable problems. From that effort arose Soviet communism, with all its pros and cons.