Didn't see the finish of the race, but from what I read it sounds like he was being "pushed"... But a inch or two over in the wrong direction can send the "push-ee" into a wreck.
Just watched the replay on youtube; he was blocking, came down in front, that's what set everything off.... Looked eerily like the crash that killed Dale Earnhardt; he went headfirst into that wall; those safe barriers that they put up after Earnhardt's crash might be what saved him. He's probably got some head trauma and some internal damage from getting t-boned in the side at 180 mph.
Weird thing is, I've always expected dudes to walk away from crashes after I saw dude survive this one in a truck race at Daytona:
I was convinced I had just watched someone die