Complex sentence: When the base changes, a revolutionary class becomes the new ruling class that forWTF SHUTTT UPPPch the superstructural elements of society propagate, then become the governing ideology of the historical period.
Split into simpler sentences: When the base changes, a revolutionary class becomes the new ruling class that forms the superstructure. These ideas, which the superstructural elements of society propagate, then become the governing ideology of the historical period.