Board Thread:Show-Related Questions and Answers/@comment-24243167-20131224102233/@comment-5106672-20140123030340

Or maybe, since the dagger was touching another person while the Dark One was being stabbed, it counted as if he was the next Dark One. I mean, the Dark One powers need the other party not necessarily to actively kill the current D.O. to pass on, but simply someone else touching the dagger while that happens. But since both the former and the new D.O. were dying at the same time, poof, they vanished together.