He took three strides before the hit, charging is accelerating to make a hit from a distance.
Charging definition: "Charging in hockey is when a player charges an opponent and makes contact with them, whether it be by skating, or jumping, into them. This can occur anywhere on the ice, and what differentiates it from a standard body check, is the distance traveled to make the hit.
The general rule of thumb is that if a player hits another from three or more skating strides away, it will likely be called a charging. However, it is at the referee’s discretion to determine what that “distance” is."
He went from his blue line to on the other side of the red line, while gaining speed. A clean open ice hit cannot accelerate into his target. He was clearly accelerating into his target.