How would they build these things? In a practical sense? The world has moved entirely virtual. Humans are able to achieve their every dream in another reality.

How would they build these things? In a practical sense? The world has moved entirely virtual. Humans are able to achieve their every dream in another reality. They can even make dyson swarms, on their own, and fly with it, in VR. But in the real world? Actually make a Dyson Swarm? Elon Musk is trying to go to Mars with the help of thousands of people directly and the indirect help of hundreds of thousands of people. It takes a huge collective effort for an engineering task so big. Yeah, sure there might be a few 'real worlders', but it'll be a lonely place out there on their own, they'll have no infrastructure, no backing, nothing. So while they may want to build that Dyson swarm, they won't be able to. There might even be all sorts of laws in their way to make sure no-one can spoil it for everyone else by eating up resources unnecessarily or putting others at risk. As for your side note, the speculation was about what's most likely, not what's possible. My point is that while Dyson swarms might be theoretically possible, my belief is that they're not practically possible because by the time you reach that level of technology, society will have already moved to a different reality. And mine is a speculation just as much as the GP's.