You footstooled him when you ledge dropped, watch some of the other similar videos, he doesn't show the footstool animation because his upB has "juggernaut armor". he also doesnt have to upB again immediately after the footstool, but instead can wait until that upB is used up.
The cypher explosion is just the normal animation of an unused cypher when you take out another cypher, UpB from the ground, drop immediately and UpB again, you'll see your explosion.
This was all figured out yesterday in the brawl tactical discussion section.
I don't take credit for knowing about the cypher explosion animation, somebody else posted that yesterday.