Some geometry of the shots. Note; the shot interval between shot 1 and 2 is 6.3 seconds and between 2 and 3 is 4.9 seconds... not really that fast.
For the last shot the target would appear to be barely moving just slowly increasing range.
That's a very interesting study. Haven't had time to digest all of it yet, but it's a great analysis of the mechanics of the shots.
I think that time interval comes at you a little faster than it looks on paper. No, not terribly fast but certainly not helping accuracy.
Mainly I am thinking that the equipment and ammo was a significant hindrance, and while Oswald's skill set was adequate- it was not enough to overcome the limits of the equipment. The biggest factor may have been 'luck'.
Rifle is 3-5 MOA accurate. Let's call it 4 MOA.
Under time pressure, top match shooters are getting getting ~3 MOA groups in the 10-ring at similar distance but with 1 MOA or better rifles.
Military shooters that are not big match guys are probably getting at best 6 MOA under time pressure with a 2 MOA rifle? Just a swag there.
I think Oswald's capability would be 4 MOA at best, add 1 more MOA for moving target difficulty.
All aspects considered, Oswald was going after the target with 8 to 10 MOA capability.
Of course this is all BS cooked up in my head but it is based on observations of many different people of varying experience and capability putting holes in paper under time stress. I think I'm at least directionally correct in saying no, this was not an easy shot for Oswald. At best it was a 'lucky' shot for him, though 3 shots to make a fatal hit make it very plausible to have happened- dare I say even probable?
Here's a digital rendering of the two bullets that hit, fatal one fragmented. This was done by a collaboration between the National Archives and the NIST. Keep in mind that analysis of the lead core showed nil antimony, which would make the lead very soft. I'd expect fragmentation in any bullet that connected, so the mostly intact one is curious. Maybe it first passed through something soft that slowed its velocity.
source:
Bullets That Killed John F. Kennedy Immortalized as Digital Replicas