>>6197679China and Russia were still feudalist while all the other empires were capitalist, literally everything was broken and non-functional during and after the civil wars in both countries, and it took the communist party of each nation a whole lot of effort to make something out of nothing.
Just think about it, the USSR had most of its infrastructure damaged in 1922, and even after World War 2 destroyed what they built west of Moscow, they still sent a man to space in 40 years before the world’s then-only superpower (USA) did.
There’s also Cuba, and the short-lived Sankara-era Burkina Faso.