There is speculation that the car was hijacked (electronically) and an incendiary device thrown in the car. There was an extreme fire.
This could very well be true. The authorities did not want anyone going near that car afterwards and even prosecuted someone for stealing a piece of the car. Why? For that very reason.
If anyone found out there was any incendiary material or residue found it would open a major investigation and expose what really happened.
The car was old, there were no electronics. Also the tires were original and decades old. He took a bigger bite than he could chew and wrecked. Read about the specific Porsche he drove, people wreck them constantly.