I’m going to be honest, here: I watch stuff like the Krypton trailer, and I think to myself Why the heck didn’t they just all move?
The Superman origin story makes more sense when you don’t actually show people what Krypton was like. If Jor-El is just this weird crank out in the wilderness somewhere, then it kind of makes sense – or at least doesn’t strain disbelief so much – that the rest of his planet was ignoring him until it was too late. But once you start giving everybody an aircar with reactionless thrusters and forcefield-dome cities you’re going to get people who will combine the two with the FTL drive that Kryptonian science has obviously discovered and then go all Cities in Flight as soon as the planetary quakes start getting seriously problematical.
Or, you know, they could have maybe already developed an interstellar civilization? Maybe even gotten their own dang Green Lantern assigned to their sector, because the Corps is part of DC canon, too? – Yes, I know that this is a topic that has been discussed by comic book fans, but we’re talking about SyFy network executives, so maybe the thought hasn’t percolated upward yet.