What phenomena in the economic and social development of countries in the XIX century were reflected in the theory of scientific communism?

The theory of scientific communism was to a large extent the heir of numerous ideas of “universal equality”. Of course, the attention of the bearers of such ideas was immediately attracted by the appearance of the proletariat and the rapid growth of its numbers. Thanks to their working conditions, the proletarians were more developed than the peasants, better organized and easily manageable, and at the same time the proletariat (especially where it was just beginning to form) was still too immature and lacked sufficient political culture. All this made it easier to propagate radical ideas among the workers.
Scientific communism, calling for the forcible liquidation of the “exploiting classes”, focused exclusively on the proletariat. But in the middle of the XIX century. even in the leading industrial countries, the proletarians constituted an absolute minority of the population.