I saw the video. Kid got out of his car. His fault. Steward tried to send him a message and overcompensated. Kid dead.
Fault: Kid
Tantillo in this upcoming quote is the County District Attorney that took the case to the grand jury:
Tantillo said that Stewart did not change course as he passed Ward and that the fishtail movement of his racecar seen on a widely viewed video of the accident came at impact and was a result of his cars hitting Ward.
Steward tried to send him a message and overcompensated.
...
I highly doubt Stewart even did that.
Some thought that Stewart gunned the engine which caused the car to contact Ward.