I don't know and see how Krav Maga became ineffective against MMA. IMHO, Krav Maga is the most effective, practical, and efficient MA/self defense system there is to date. It's principles and techniques are very simple yet very effective and deadly. It doesn't employ very difficult maneuvers in defending one's self.
Krav Maga is reality based, not sports or studio type based of training, which makes it very practical especially in defending one's self on the streets and outside the ring and dojo.