Lenin held it as the "highest stage of capitalism"

That book was written by Vladimir Lenin, who split Russia into several states, forming the Soviet Union.

capitalism

engels

Imperialism, according to most proponents of its causes, is the final stage of advanced capitalism. There was no advanced capitalism until the end of the 19th century. Even Adam Smith wrote about capitalism only in the late 18th century. Smith had no predictions on how capitalism might develop into imperialism.