Note: This version of Kandor was actually just a psychic manifestation created by Saturn Queen.
The real Kandor was not discovered until quite some time after this event.
Some of us try hard to make the world a better place than it was when we found it. When Brainiac returned to consume Argo City, Kara's parents had no choice but to send her in a rocket headed for Earth.
After Brainiac's attack, Kara's father created a force-field around Argo using a Brainiac Probe.
(For now at least.) Kara-Zor-El, also known as Supergirl and Linda Lang, is a Kryptonian superhero based in Metropolis.