If I had to guess, I'd say he had low tire air pressure. I bought a used Triumph Daytona a few years ago. Driving it home I almost went off the road in a turn, as this guy did. I managed to get it stopped. Found out the bike had been sitting for a while, and the tires had about 18 PSI of air in the tires. Had problems negotiating curves, untill I got to a service station and put proper amount of air in the tires. MAINTAINING CORRECT TIRE PRESSURE IS VERY IMPORTANT. In the video it looks as though the guy was experiencing the same problem I had, except he panicked instead of stopping.