Still doesn't make sense. The PLA (largest army in the world) can't even capture Taiwan. If they wanted an impenetrable fortress a random island is all they need.
The movie Elysium shows this ruling class in space, proletariat on Earth, scenario in very high fidelity. The movies itself is just OK, but the glimpse of this future is very well executed in the production design and special effects. https://en.wikipedia.org/wiki/Elysium_(film)