I'm in mobile and don't have access to my notes or books, so I apologize for the less-than rigorous response.

What you're asking about can essentially be restated as "Why does communist in practice not adhere to Marx's presentation of dialectical materialism." As I imagine you know, Marx says society moves from antiquity to feudalism to capitalism to socialism/communism. As you also seem to understand, capitalism will inevitably begin to manifest itself as industrialization, for reasons he makes clear in Kapital. Inevitably, Marx reasons, as capitalism continues to deprive the laboring class of both its species-being and true value of the cost of their labor, the laboring class will rise up and seize the means of production. They will institute a dictatorship of the proletariat, then communism will appear somewhere on the distant horizon.

Of course we know this prediction to not have unfolded like that at all. As Western Europe and America continued to industrialize, you see the increase in colonization and the sort of imperialism whose scale Marx hadn't fathomed, nor even truly considered until his last years. This in turn meant that while the colonizing powers enjoyed more growth and more wealth, the colonized became even more impoverished and left behind. Marx didn't account for the fact that capitalism could also be regulated by the state to agree that allowed for an increase in living standards for most of the laboring class, which had the effect of appeasement; the proletariat was fed, clothed, and bedded, and therefore had no need to revolutionize.

The promises of socialist utopia was much more popular east of Germany, where many nations, notably Russia, were still feudal. There were millions of peasants that frequently starved. They were, in short, more captivated by the promise of liberation through revolution. This is why Lenin (and Trotsky and later Stalin) were successful in initiating the Bolshevist revolution of 1917: Russia was hemorrhaging support among the people for the War, the nobility was hated, and people were starving. Lenin took it upon himself to be the "subjective element" (I forget how it was exactly translated in his What is to be Done) in the unfolding of Marx's theory of historical materialism, and so triggered the revolution.

What does this say about Marx's theories? It's hard to say, because, indeed, Lenin (and Stalin) seemed to think one could jump from feudalism to socialism by taking control of the state and then coordinating its industrialization. History has shown the terrors of this endeavor, it being not limited to Russia but to China as well.

The short of it is that, like all things, the implementation of such a systemic theory of society will inevitably produce results that differ from one's hopes. As for why that is, is a question best left for r/AskPhilosophy.