Other than the big two most ones fell due to being actively undermined by the first world, assasinating it's leaders, arming ISIS style rightwing paramilitaries and so and so forth.
The USSR besides it's reign of terror during Stalin showed that you don't have to wait for a society to become an industrialized one before socialism. Besides you'll have cut the line of supply of surplus value from the thirld world to the first, people being bribed with social democracy will stay happy with their bread crumbs.