What I'm seeing is bump drills are very necessary. Rough ones where there is a speed differential. Your elbows should be firm but bouncy along the bend, and completely supple laterally, like your elbow should be able to swing a bit, like a pendulum, while maintaining the bend. My mentor from my first couple years of riding used to knock my elbows around just randomly on rides. It's ok if your bars move with a bump, but you need to be supple enough that it's dampened and brought back smoothly.
I think that what happened in the video is that this guy bumped bars to bars or bars to elbow. The resulting countersteer stood inquisitor up and sent him possibly across the other guy's wheel, but more likely just into a high-side crash out of the corner from the inertia of being stood up with the centrifugal force of the corner helping. The other guy got the opposite countersteer effect, and it would have just tightened his turn up. Since this corner wasn't at the limit, there was traction available to turn tighter after the bump.
Most crashes seem like someone else's fault, and that's often true, but you can't get hung up on it. You wouldn't have crashed if you didn't sign up to race. The responsibility starts there. You could have been tightly drafting a rider, which would protect you a bit more. You could be more prepared for such expected contact. I went 19 years since my last crash, then went down last season when a guy sprawled right in front of me and I had nowhere to go -- I still blame myself 100% for not having the fitness or tactics to be up at the front of the race. My crash was my fault.