Think of it like this: Silicon Valley is probably one of the richest bits of America. So imagine that some dictator decides to invade it, and that the US military try to stop him but fail in some improbable way. So this dictator now controls a bunch of ruins with no electricity containing broken computers. His troops are herding the geeks who used to program those computers into internment camps. How does this make him any richer than he was before?
If you conquer a third-world country then you can exploit its raw resources: a semi-literate population, farmland on which they can grow food, and maybe minerals they can dig out of the ground. That was essentially the thinking behind the Heartland Theory (see link). But it just won't work any more. These days the real wealth comes from brainpower, but you can't capture that wealth by pointing a gun at someone.
https://www.worldatlas.com/articles/what-is-the-heartland-th...