Let’s back into this...
He was aiming at a crowd of 22,000 that is, roughly. 400 yards away and 320 feet below.
Let’s assume 4 square feet per person in the venue, that’s an 88,000 square foot target at 400 yards and below you.
I’m not going to do the math here, but I’m going to invoke the ‘inverse square rule”. (I’m an engineer.). Basically, for half the distance you quarter the target.
A reasonable equivalent is hitting a 5,500 square foot target at 100 yards. Like hitting a large home at 100 yards.
With a smooth bore shotgun, iron sights, and cheap Winchester silver box slugs I can manage a 5 inch group at 100 yards. I bet I could hit a 4x8 piece of plywood (48 square feet) almost as fast as I could work the action.
His target was 5,500 square feet at 100 yards.
=> this was no feat of marksmanship.
And, I do get that the target is plainer and angled away and therefore smaller...but not much!