Board Thread:Questions and Answers/@comment-138.130.106.201-20140801110937/@comment-6697950-20140801111519

This question has been answered many times. Heathcliff/Akihiko turned off the mechanism that triggered the NerveGear to fry the player's brain (most likely before the duel, as he wouldn't have had time after it). He did so because he wanted to speak to Kirito after the battle, thus he created a special space outside of Aincrad where they could meet. Because Akihiko was defeated, he likely let them live as a reward.