Any research that threatens to repeat those events is outlawed. Technological progress on both planets is covertly slowed down.
Wow! I have to say, this is the smartest rationalization about why Kryptonians didn't allow space travel that I've ever seen. They went to another solar system once, and they
knew what would happen if they left the red sun. It would also make Jor-El's sending Kal-El to Earth all the more interesting if he was privy to the secret knowledge and also knew he was creating a super-being in sending his son there.
Which begs the question as to Jor-El's intent: was he attempting to create a super-being simply to give an infant the best chance of survival? To create a force for good? Or perhaps even to create a galactic dictator?
Dakota Smith