There's a letter towards the end of his life where he speculates about Russia, specifically, skipping the capitalist stage because of cultural reasons.

Arising from a capitalist and industrial system is less of a requirement and more of what he considers to be the most likely scenario. You could, for example, in theory have a peasant revolution but you'd either need to attract industrial expertise to modernize your factories or reinvent a lot of wheels.

And, of course, Marxism isn't the only socialism.