I knew a man who died in a similar accident, many years ago. He was having a heart attack, and as a result he unintentionally pressed the accelerator pedal to the floor, rigidly gripped the steering wheel and was only prevented from becoming airborne into the river by rear ending a loaded haytruck at approximately 90 mph.
Probably about the same as what happened here. In both cases, good that no one else was in the car, and no one else hurt.