[Kazu-kun]

Originally Posted by styr

@Kazu-kun

It isn't explained in the beginning of ep5 (yay timeskip),

Spoiler for ME1 spoilers, again.:

but the events of what happened after the meeting+duel between Kirito and Asuna is what directly led to the boss being killed. Asuna stayed up late thinking about her loss to Kirito and triggered an NPC flag/event that sang her a lullaby which contained a clue that the boss could be put to sleep. She never got a chance to try her plan since the lullaby plan worked the next day after finding someone with high musical skills.

It's not timeskip, it just didn't happen. It would be different if they at least hint that all that did happen, and maybe they will later on, but for now we can't count on that.