The reason why Storm stayed made sense. Alot of the veteran X-men who embodied Xavier's original dream left. Kitty, Bobby, Beast primarily. On Scott's side left are a bunch of former villians. She's not staying bc she agrees with Scott, but more to keep him in check and make things dont go further downhill then they already are. The Utopia side isnt going anywhere but it doesnt have to be the same militaristic, shady methods, type of way its been existing as. Storm is there to balance things out and help keep them legit.