The "Kryptonians don't want to leave their world" doesn't make sense in any continuity with Brainiac in it.
While xenophobia would be a normal response, the reaction to a whole city being abducted by an invader isn't usually passive isolationist xenophobia.
It's more like, "this is a day that will live in infamy, now let's go murder every Coluan, especially the babies."
But there are so, so many problems with Superman's origin, specifically Krypton, that the "why don't they just leave" issue is only one thread of the rope, which also includes:
1)why did Kryptonians evolve powers that function under yellow sunlight when their sun is red?;
2)planets can't explode;
3)related, stars capable of sustaining life do not go supernova;
4)also related, what kind of red star has a life-sustaining planet orbiting it, anyway? (this objection is subject to the outcome of present-day scientific investigation, but red giants are obviously out, and my understanding is that red dwarves would tidally lock any planet close enough);
5)it strains belief that a civilization of hundreds of millions or billions could ever act as unanimously as generally portrayed in regards to Jor-El's warning;
6)what kind of fuck-up explains how the Daxamites wound up vulnerable to a common element, instead of a fakey, rarer one like kryptonite? (I mean, I know the story, but oops doesn't even start to cover that);
7)how long was Superman in transit? it's usually portrayed as a brief interval, but the existence of FTL tech on Krypton really, really militates against any lack of a relocation option.
8)related, if Jor-El, the geologist and apparently also spaceship designer (yeah, whatever), knew that yellow sun radiation gave Kryptonians superpowers, then this was almost certainly well-known by biologists--and if so, I'm pretty sure we just found an economically compelling reason to colonize other planets, dudes. How much would you pay to get to Alpha Centauri if it gave you the ability to shoot death lasers from your eyes, fly, and live as a functional immortal? I mean, at least fifty bucks, right?;
9)there are continues where Jor-El invented the Phantom Zone (because geology, astronautics, and biology ain't enough, we add dimensional physics--our friend Jor-El is a highly qualified Kryptonian)? Is Kal-El's dad the universe's greatest monster?
Now these problems are all soluble, but not without rewriting the hell out of the existing material, since no single Superman origin of which I am aware significantly bothers with them. The LSH cartoon, however, gets points for depicting Krypton as merely dead as a result of its vulcanism, instead of blown to smithereens.
While xenophobia would be a normal response, the reaction to a whole city being abducted by an invader isn't usually passive isolationist xenophobia.
It's more like, "this is a day that will live in infamy, now let's go murder every Coluan, especially the babies."
But there are so, so many problems with Superman's origin, specifically Krypton, that the "why don't they just leave" issue is only one thread of the rope, which also includes:
1)why did Kryptonians evolve powers that function under yellow sunlight when their sun is red?;
2)planets can't explode;
3)related, stars capable of sustaining life do not go supernova;
4)also related, what kind of red star has a life-sustaining planet orbiting it, anyway? (this objection is subject to the outcome of present-day scientific investigation, but red giants are obviously out, and my understanding is that red dwarves would tidally lock any planet close enough);
5)it strains belief that a civilization of hundreds of millions or billions could ever act as unanimously as generally portrayed in regards to Jor-El's warning;
6)what kind of fuck-up explains how the Daxamites wound up vulnerable to a common element, instead of a fakey, rarer one like kryptonite? (I mean, I know the story, but oops doesn't even start to cover that);
7)how long was Superman in transit? it's usually portrayed as a brief interval, but the existence of FTL tech on Krypton really, really militates against any lack of a relocation option.
8)related, if Jor-El, the geologist and apparently also spaceship designer (yeah, whatever), knew that yellow sun radiation gave Kryptonians superpowers, then this was almost certainly well-known by biologists--and if so, I'm pretty sure we just found an economically compelling reason to colonize other planets, dudes. How much would you pay to get to Alpha Centauri if it gave you the ability to shoot death lasers from your eyes, fly, and live as a functional immortal? I mean, at least fifty bucks, right?;
9)there are continues where Jor-El invented the Phantom Zone (because geology, astronautics, and biology ain't enough, we add dimensional physics--our friend Jor-El is a highly qualified Kryptonian)? Is Kal-El's dad the universe's greatest monster?
Now these problems are all soluble, but not without rewriting the hell out of the existing material, since no single Superman origin of which I am aware significantly bothers with them. The LSH cartoon, however, gets points for depicting Krypton as merely dead as a result of its vulcanism, instead of blown to smithereens.