I can't imagine all his hair helped the fit. But after watching the replay a few times you can clearly see the chin strap tore off the other side of the helmet. The impact was very intense. He appears dead sliding across the track. So
I'll stick with my original statement. No Helmet would have saved him, I don't think his hair was a cause of the helmet coming off. It was caused by the chin strap failing. I'm not calling into question AGV either. What I want to know is how his bike shot back across the track. He appears trapped under the bike, was his hand trapped with the throttle open? So very sad.