The Elder Wand specifically goes to whoever defeats its last master. If Draco had any other wands going, they wouldn't have switched unless they were personally removed from Draco.
Possibly Voldemort didn't notice that it wasn't working because he thought it would work now. Power of positive thinking. Also, I don't think he got a huge amount of time to use it between killing Snape and getting killed; he thought that it successfully killed Harry, and he didn't do much other powerful magic IIRC.
The Elder Wand specifically goes to whoever defeats its last master. If Draco had any other wands going, they wouldn't have switched unless they were personally removed from Draco.
I see, so that's how it works. Still feels a bit forced though.
If merely disarming someone counts as defeating them, then knocking someone the eff out should count as defeating them as well.
Spoiler:
I think it was because the wand itself did no damage to Harry at all. It killed the fragment of Voldemort's soul, and that briefly dragged along Harry's soul for the ride because of the way they're bound. Harry getting knocked out wasn't directly caused by the wand or Voldemort, it was a side-effect.
