The video: https://youtu.be/rVi5wccLCAg
The poster of this is long gone but I wanted to comment, since there's a lot of discussion about the board doing something weird. I didn't read all of the long thread, so hopefully I didn't miss something.
I think he just lost his balance and fell.
He's riding on a fairly busy street, in the bike lane, filming himself, looking the camera, looking at the street. Then he wants to pass some girls on bikes, he wants to keep himself in the shot, get the girls in the shot, looking at his camera, looking at the street, trying to look cool, maybe even trying to make eye contact and smile at the chicks while needing to keep track of all this other stuff.
Then he moves into the traffic lane to get his cool shot. He'd almost have to look backwards to make sure he's not going to get hit, while keeping all this other stuff in mind. Right away he falls.
I hate looking backwards, and I do it quickly and I tend to lose some balance. I hate it so much, I think I try and convince myself I can risk not doing it and I put it off and then I have to look and I have to do it really fast. This debate with myself lasts a split second. I destabilize a little or a lot.
Anytime I'm not constantly scanning the ground and I hit even a tiny bump, and I didn't see it, my brain can't process how to react anywhere near as well as when I'd seen the bump, looking backward makes it much worse.
If he hit a little bump or not, I think his brain got confused when he looked backwards and his body did something his brain didn't intend and something the board didn't like, such as pushing the front left corner down, and he just lost his balance and fell off.
You can easily hear the engine straining away, trying to provide as much speed as he is asking for, but he simply reaches the limits of what the board is capable of.
@kelp This is exactly right. That humming sound is the nosedive warning if I've every heard it. He's probably well beyond pushback most of the video.
I can't decide whether you are making fun of me or not.
That's scary, it doesn't sound that loud to me, I'll need to pay more attention when I'm riding, I may be doing the same.