Contra Marx and his latter-day epigones, it is not class struggle that shapes political and economic systems. Rather, it is the change in the what asset classes constitute main stores of wealth that determines shifts in the relative power of economic classes, and eventually of social classes.
For the ancient Romans of the Republic and early Empire, wealth was stored in land and slaves, and consequently it was the great families who occupied the pinnacle of power. When medieval Europe dispensed with slaves and — because of declining manufacture — increased importance of land produce, it was the feudal lords who migrated to the top. (By contrast, contemporaneous West African kingdoms used slaves as the main store of wealth, with predictable results when they eventually encountered European traders.) As manufacture, money and exchange gained in importance, it was the turn of the mercantile and trading classes.
Despite experiments in police-state power structures of the big “isms” of the last century — themselves in essence being attempts to revert wealth basis back to land and slave-holding — their failure to abolish money served to ensure the reaffirmation of the primacy of capital in power relations. A question often asked is what comes after Capitalism. No measure of earnest theorizing can return an answer until it becomes clear that a new wealth basis is stirring in its cradle. Much ink was spilled on arguments that new riches will be based on reputation, or intellectual achievement, or moral virtue, or else fame — but the fact remains that all of these have value only in terms of their monetization, and until a new and universal measure has arisen, no change from Capitalism can be reliably divined.