Are you not disputing the suspect vehicle had time to rev his engine and break traction at nearly the point of impact with the victim?
It could also be the fact that nobody expects to see a guy walking down the track in the middle of a race.
A slight issue with your comment here.
Did the suspect driver not know a quick lap prior he had sent the victim vehicle into the wall?
Should this have not caused the suspect vehicle to proceed very slowly as you come around the track, knowing damn well there could be debris, vehicles or victims on the track?
I've seen many incidents where a driver gets out of his car to shout at somebody, but I've never seen someone run around on a dark, dimly lit dirt track, in the middle of a race, where the rest of the field is taking laps under the yellow flag.
Nobody will ever know what was going through Stewart's mind at that moment, except for Tony Stewart. Maybe someday he will say something about it.
The young man snapped and did something very foolish which forced at least one other driver to swerve to avoid hitting him.
Unless some compelling evidence to the contrary appears, it's pretty clear that this young driver caused his own death.