I don’t know if any of you have watched “Top Shot” on the History channel, but it’s a shooting competition that often requires shots much more difficult than what Oswald accomplished.
Have a look at the section starting at about 27:00 in this video. This was a speed competition, where the contestants had to run up a hill while stopping at four stations along the way. At each station they had to pick up the weapon, load it, adjust the sights if necessary, then shoot a target downrange before going to the next station. The target is about the size of a human head.
The first station was a pistol shot at 50 ft. The next station was a rifle shot from 100 yards, using an HK93 with iron sights. The third station was a shot with a Mosin-Nagant scoped rifle at 125 yards, and the last station was a 150 yard shot with an SVT-40 scoped rifle.
Bear in mind that these guys are having to do this under physical exertion, where your heart is beating madly and your breathing is hard. The first guy up hits 4/4 targets with a single shot each. I added up the times starting from when he was finally in shooting position behind the rifle, and the three rifle shots together took him about 15 seconds - all from elevated positions, all at ranges farther than Oswald’s shot. If you start counting after the first rifle shot is made, we’re down to 11 seconds. And this from a shooter who had no time to practice the exact shot and who wasn’t familiar with any of the weapons.
So, removing the time required to climb the hill and load the weapons:
The next guy went 4/4, with the time between the first shot and the last about 10 seconds.
The third guy goes 4/4, with the time between the first and the last about 7-8 seconds
Fourth guy, 4/4, about the same time
It wasn’t until the fifth shooter that anyone even missed a shot. At much longer ranges than Oswald’s shot, under heavy physical exertion, shooting rifles they weren’t familiar with. Oh, and there was a fairly stiff breeze blowing, too.
Oswald’s shot was just not a problem for a halfway competent rifleman.