Marx also thought the idea of a Revolutionary vanguard was wrong and impossible. He was a bitter enemy of another socialist named Blanqui who advocated the need for a group of professional revolutionaries to lead the way. Lenin did exactly what Blanqui said and ignored Marx, who thought that some spontaneous revolution would happen and a decades long struggle would result in victory.
Where exactly do you get that notion? Please try to find that in Marx’s own writings and not the opinions of others that are not based on what Marx wrote. This “vanguard” manifested in the personage of a communist party itself and whatever paramilitaries aid them; there can be no other definition, certainly if the goal is a revolution to seize power. (And why did you capitalize “revolutionary”?)
Marx also thought the idea of a Revolutionary vanguard was wrong and impossible …