Originally Posted by
FUBAR007
Attilan was, for most of its existence, an isolated, secret society. It didn't war with the human world. It didn't interact with the human world much at all. Its exposure to the human world was basically "here's this isolated nation that's been there all along; we just didn't know about it."
Krakoa consists of people who grew up in human societies rejecting those societies and forming their own. First, it's a rejection of human civilization. Second, it's artificial--mutants aren't a lost tribe who've been living off on their own all along. Third, Krakoa's leadership includes genocidal mass murderers (i.e. Apocalypse) as well as people the human world regards as murderous terrorists (i.e. Magneto, Exodus).