Stewart has a legandary temper. It looks to me like he was trying to "buzz" the 20 year old kid, spin a little dirt up on him as he went by him under the caution. He was CLEARLY going faster and taking a higher line on the track than the other cars during the caution. And he was definitely on the throttle hard as he hit the kid. I'm not sure if the car got away from him as he accelerated or the kid was closer than he estimated but I think Stewart was definitley trying to fuck with the kid as he went by him.
Stewart will no doubt say he didn't see the kid. That is a plausable defense and will keep him out of jail but I seriously doubt it's the truth. Only Stewart really knows for sure.
THIS.
Stewart is a bit of a psycho, which has served him well in racing. No family, just racing and intensity and will fistfight at the drop of a hat. Makes him an awesome driver. After killing a man, he's racing today without missing a beat. He's probably eating eggs and bacon right now, watching some Netflix, giving no fcks about the drama surrounding the incident.
He did hit the throttle. He did turn his vehicle toward the man on the track. The other drivers, on the same arc, managed not to do this. I'd say he was just trying to bump the kid because, well, the kid was talking shit and Stewart may have thought the kid needed a lesson.
None of the ESPN analysts will say it - but none are saying "we know this is something Stewart would never do intentionally". They're just waiting. One of the monday AM pundits will get brave and say what everyone is thinking, and probably get a week ban for it.