As Simon Kinberg noted when speaking with Empire about the Dark Phoenix trailer, Jean Grey goes there to seek Magneto’s help since he’s had quite the violent past.
If by some chance the main X-Men series continues, it would be interesting to see Genosha grow and become more self-sustainable, but then again, who knows how long we’ll spend there in Dark Phoenix.
Like its comic book counterpart, Dark Phoenix’s Genosha is an island, but this community is just getting started and is a far cry from the nation depicted on the printed page.
But once Jean loses control and becomes the Phoenix, it looks like Magneto will leave Genosha and form his own group to stop her using more drastic measures than what Professor X and some of the other X-Men are willing to use.