Easy: the western elites read Marx and took him far more seriously than the western Marxists did. Thus they de-proletarinazed the Imperial Core, and left the mass of productive workers to the actually Marxist world, who built them readily.
I asked this question at 9 years old growing up in a Communist family before the fall of the USSR. It is the only real question in Marxism.
Now the riddle of MMi circuits...
Why is there no revolution? This is the question that must be asked. Please tell me. I believe that the rational is the real, so I believe implicitly already that there is a rational ground for there being no revolution.