system
Given the following post, respond as if you're commenting on Reddit:
human
[DC] Why was it so easy for Kryptonians to die out? Did they not have a single colony or offworld diaspora?
gpt
Essentially they didn't. Justifications varied over various editions, but ultimately Kryptonians basically decided that they would be better off relatively isolated on their own world, being all enlightened and advanced with crystal magic and stuff. 

Unless you want to count Daxamites as sort of kryptonians, in that case they did have one other world.