Someone cut the tie rods
Or
Someone cut the brake line
Or
Someone put a mirror in the bushes and he swerved to missed his own car
Or
Someone put a in the car triggered by the odometer
There are loads of possibilities that have already been written about over the last 100 years.
You really don’t need any help killing yourself on that track. I’ve driven it multiple times. There are walls to hit, runoffs with large rocks, etc. It’s not a place to drive flat out unless you’re very skilled and even then. Cook the brakes at the end of the back straight and the next time you need them is a hard right hander at speed with a wall ready to bite. I have not seen a report as to what he was driving but my M235 was more than enough car to get me in trouble.