Changing material conditions to foster the development of a proletarian class is a solid theory of how to build working class power and consciousness. You might deride it as just infrastructure, but the workers who maintain and transport goods on that infrastructure (as well as the people who provide goods and services to those workers, and so on and so forth) now have more economic power and ability to organize in solidarity with each other than subsistence farmers would have against their landlords. And before anyone can build, say, a tractor factory, there must first be adequate infrastructure to supply said factory and take its finished goods to internal as well as potentially foreign markets.