Ok, here's my best CSI at it:
Kids wanted to make funny video.
The idea is to pull the table cloth out, pretend to knock the blonde kid into the shelf unit and fall over like he is knocked out/hurt.
End funny youtube video.
Here's where it gets interesting.
What they didn't plan for is the impact to be so great that is knocks the shelf unit's center of mass out of its perimeter of stability, thus making it fall over.
The blonde kid, being a good actor, follows his plan and falls on the floor assuming it is going to be hilarious, but he doesn't know the self unit and television and falling ready to crush his fragile body.
Looks like the only channel on that TV.....
is the murder channel.