He was a brilliant driver in a car he had a lot of experience with. (IIRC he was a Ruf test driver) That was an amazing car with just far too much power in relation to how much traction it had, hence the sliding around and constant recovery from sliding around. A 500hp twin-turbo motor in a modified narrow-body 911 chassis without the super wide tires in the rear like you'd see on an older, wide-body factory Porsche 911 turbo. (they opted for low weight and better aero over traction)
That video makes other Nurburgring videos look a little tame by comparison. The car held the (street car) record on that track for a while.