Vibrant new realms can only spring up if there are people in the area ready to take advantage of—or even cause—Morek's collapse. And it can't just be any old power-hungry nobles, if you want the new realms to be viable: it needs to be people with a significant following, and with a solid idea for how to run a new realm.
Old, large, inactive realms don't just collapse into a bunch of new, small, active realms spontaneously. The most likely thing to happen is for other old, large realms to bite chunks off Morek and grow larger themselves.
If you want there to be a vibrant, new realm in Morek's lands, you need to come up with a solid idea for a new realm, put yourself in Morek's lands (which is to say, in Morek) and start making friends.
(And I would caution that "a solid idea for a new realm," contrary to what seems to be popular belief, doesn't need to be something amazing, new, and cool. It's actually better for your long-term viability if it's something relatively conventional. Too many people try to do something nobody's ever done before, and just end up being kind of weird. And this goes double on Dwilight, where you have to stay within SMA.)