I'm with ray h and Capn Kirk on this one. Way up before the curve he does a little bounce which might have set the chain off which at 1:17 is clearly off. But instead of noticing the change in engine braking /traction he then gets busy waving ( actually as he should be really setting up his line, which he doesnt do so well). It seems he realizes he is going in too hot or has no feedback from his engine, tries to trail brake, locks the wheel and the rest is pretty clear.
Invader I couldn't quite get where you see his right foot move.
It could happen to anyone. Being sloppy I mean.
"Only two things are infinite, the universe and human stupidity, and I'm not sure about the former."
- Albert Einstein (1879-1955)