I'll take a good faith stab at this, then.
In plain English: Every overthrow of the aristocracy (or equivalent class) comes from the people just below the aristocracy with the aid of people at the bottom, who by nature of their class are simultaneously the most populous and the least prosperous and have only to gain from overturning the established order. Once overthrown, whoever was next in line, in terms of capital, establishes themselves as the new aristocracy. The nature of the overthrow involves "enlightening" the proletariat, usually in the form of increased industry, education, and technological potential. However, this shift also sends more people into the proletariat. The cycle continues gradually leading to the creation of two pen-ultimate classes, the proletariat and the bourgeoisie. Once this final revolution destroys the final class relation, class antagonism is dissolved.
This is Marx's "dialetical materialism" in a nut shell.
Indeed, although Marx got it wrong by basing his analysis on Locke's labor theory of property leading him to base his dialectic on capital stock rather than power. Further it is not "the people just below the aristocracy", this is another one of Marx's blind spots, the inability to clearly see central power or "The Minotaur" as Jouvenel put it. The true dialectic is the "High" of society allying with the "low" to destroy the "middle" imo. That is central power outmaneuvers competing power centers (the church, states in the US, anything between the "high" and the "low" subjects) by as you say arming the marginalized under the purview of the latter. It might seem like the bourgeoisie is perpetuating their own destruction at the hands of the "low" but in reality these "foot soldiers" are always directed at the enemy of central power. And should they become a threat this dialectic will simply be re-targeted at the new "middle" the proletariat of yesterday so to speak, a good example in contemporary America would be the white working class.