I'd never have agreed to follow them, even if they'd asked. Not if it had meant leaving my friends and Rosa behind.

[He sounds completely certain of his decision, more certain than he's sounded this whole day.]

They left to find a new home for the Lunarians. One that would be free of sentient species, to avoid a repeat of Zemus' actions. As it turns out, most of them did not agree with his planned genocide of humans.