This is an April Fool’s joke where Elon Musk is supposedly wanting to build entire cities. I’m not so sure that’s it such a bad idea:
This list says the last major American city is Anchorage, AK founded in 1914:
It’s possible we’re out of great places to build cities given most cities exist at geographically strategic locations. There’s only so many of those.
But, as transportation gets more efficient, it’s also possible we could think about starting founding new cities where they have never been before. Could you design a compelling set of amenities compared to existing cities? I don’t know but it’s fun to ponder.