That I can't tell you. The only thing I know is that the driver was the National Champion in title (he won the tittle with a Pro 2) and it was one of the first races of the Championship.
I guess it's a structural weakness of the chassis. The hit forced the chassis to bend upwards and it couldn't handle it. There was no upper deck at the time so all the flex at to be taken by the chassis.
The guy drives really well, he's carefull and he does not crash. This was at the end of a heat (batteries drained and all) and he made a couple of laps more to feel the car. In one of them he hit a FOOT. The car didn't move and when we picked the car it was like this.
Then this thing happened. It was bad and he was really pis*** because he almost had no time to change the chassis in time for the next heat.
I'm sure that a car with an upper deck would never break like that.
But then again my Yok Worlds just shed a front shock tower mount just because a guy spinned in front of me and I hit him. There's no way to tell that these things are going to happen.
However, I guess that there were some serious shortcomings on the car design or materials that make it break like this.