What clutch? How do you know the engine sound is coming from the car on the other side of the track and not one closer to the camera and mic?
From my understanding... Sprint cars do not have a starter a transmission nor a clutch or a battery. They are essentially direct drive. They used to have a one way box or an in out box but that chore is handled by the rear end today. You engage the gear, turn on the magneto, get pushed until you reach speed, turn on fuel, start and drive off. There are no spotters and the radio is only for listening to race control. Might be a spotter but there is no during race communication.
"Clutch" was only mentioned because several posts on here said the revved engine was due to clutch/gear change. I don't think TS purposely hit the man. I think he was hit by accident. As far as picking out his engine sound, it's quite clear in the video, viewed full screen. Also, you can see the car react, and the increased tire spin. TS fans are going to see what they want to see, true or not. Fans of his style of "bravado" will do the same. I've seen him purposely wreck younger drivers because he felt they "disrespected" him (read raced him hard), and boast loudly about it on TV. NASCAR eats it up, because it sells tickets, just like they did with DE Sr. Contrary to an earlier statement, the police have stated several times no criminal charges had been made against TS pending investigation of all the relevant facts, including analyzing available video regarding the incident.
I've read reports today that his "gunning/revving the engine" just before contact has become a point of controversy, and why no declaration has been made by the investigators. The fact is, only TS knows exactly what happened, and has to live with it.