“The shooter was a pro, or very practiced and accomplished amateur.”
It was only 130 yards. That’s point blank for a decent shooter with a high powered rifle and a scope from prone position.
The amazing thing is that he missed with five shots.
The other amazing thing is that the Secret Service didn’t have a roof that close with a clear shot at the podium covered.
He was turning his head to the right, but his vertical position did not change.
If the shooter were aiming at the center of mass of the head, it would not mattered if Trump turned his head. The bullet would still have hit the center of mass, because the position of his head never changed laterally.
The shooter simply held too far left.
Interestingly, the wind earlier appears to go from left to right for the shooter's view. Maybe he was holding for wind and it stalled (Thank you Lord)
More likely he was an amateur, with pumping heart, and rushed his shot, then just hurriedly tried to get off more rounds before the SS let loose one centered on His head.