30-06 is a pretty standard hunting round,
There's two theories running around in my head
I've seen a slowed down version of the video & there is the suggestion that the bullet hits Kirk's body armor & ricochets up into his neck, i am assuming Kirk was likely wearing some kind of low profile level 3 armor under his clothes, this would be designed for considerably smaller rounds such as 9mm or 22lr, no doubt being prepared for a shooter who fancied having a pop with a handgun at closer range.
30-06 would punch right through that armor, it's unlikely the bullet would ricochet, however there is no exit wound (that I'm aware of) so the theory does have some merit as a human neck offers little in the way of mass to stop a hunting round.
Ultimately it's hard to tell in the video if the bullet strikes his armor, tumbles & hits his neck.
My other theory
It was supposed to be a headshot you're looking at the drop of the bullet over X distance, no shooter is going to risk missing in this situation by going for the throat, you're going for the larger mass.
Much like what I said in the Trump assassination attempt, you need to factor in how much the shooter would be shitting himself, you'd be shaking uncontrollably, the fact the bullet almost missed Kirk & hit his Carotid lends weight to the above.
My gut tells me this is yet another radicalised Democrat, using his Dad's hunting rifle, he would have got some firearms training through an antifa mercenary group (see Andy NGO)
However by no means is he the marksman some are making him out to be.