Reasons unknown as of yet
but lets discuss ? Detonation? Air/fuel mix problem?
I've been a volunteer firefighter for about ten years. Most of the car fires that I've responded to have involved turbocharged engines, typically factory turbos, not aftermarket ones. The reasons are simple. The turbo compresses air, so the engine can burn more fuel (produce more power). That means that the fuel pump and injection system are higher capacity. Because it's compressing air, the turbo(s) get hot. Heat cycles can loosen compression fittings. They get hot enough to ignite gasoline. Combine a hot turbo with a leak in a high-flow fuel injection system, and you get an intense fire.
I am NOT saying that happened here. That will take an examination of the remains by someone who knows what he is doing. I am saying that's the most common cause of car fires that I've dealt with as a fireman — fuel leaks in turbocharged vehicles.