Answer: Marx was convinced that discovered "historical laws" or "laws of history" (in the 19th century ideal of science was mathematics and physics which produced infallible laws, social sciences wanted to be "sciences" as well). It was of course naive, but formulation laws in social sciences was certain ideal at that time. Marx was convinced that it was a historical law - something inevitable - the conflict between bourgeoisie and proletariat. He was convinced that such a conflict makes part of historical laws and that all social classes will be reduced to 1) bourgeoisie and 2) proletariat. Consequently he believed that such a conflict (in which proletariat automatically wins) must takes place worldwide. Other revolutionarists did not have such a theoretical background.
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