Do we know what made Earth C look how it looks when callie and caliborn live there? Are the ppl who lived there and main characters now living on some other planet, or did they all uhhh die?

Callie’s Earth C is in front of a Red Giant, I’m pretty sure that alone would be enough to vaporize all the water on it and kill everything else. If the Sun Earth C orbits is similar to our Sun, then Callie lived 5 billion years after the Kids got there, literally anything could’ve happened.