The way the US gubermint convinced the public that this "mystery" has been solved is rather simple to explain. The key part is simply to show what DID happen, NOT to argue about what did NOT happen.
Most every documentary or book is involved in proving the SBT (single bullet theory) is correct. The SBT hypothesizes that a bullet struck JFK in the back (of his neck or was it JFK's back?), exited his neck, struck Connally in the back, exited his chest, struck his right wrist and then went down to strick him in his left thigh. This is shown by the RED path in the following diagram.
The RED path is the hypothesized SBT shot but the YELLOW path is the angle a shot would have taken if fired seconds later. The YELLOW bullet path is so shallow it could NOT have injured Connally's left thigh. The JFK head shot knocked him out of the way so any bullet fired later from behind would miss JFK and strike Connally.
BUT what is shown by the YELLOW path in that diagram is what has remained "hidden" for decades. Connally said that AFTER he turned to look over his right shoulder toward what he thought was a rifle shot, he felt a blow to his back. "The blow was of such force that it bent me over."
The only time in the Zapruder film that John Connally is bent over is a split second AFTER JFK is shot in the head.
Zooming in on Connally and drawing a line through the back of his head to show his head movement when the bullet struck his back, you can easily see that Connally's head moved much faster than he could have moved it especially if you consider the gubermint contends he was seriously wounded almost five seconds earlier.
The bottom line here is that the US gubermint knows that they can tell any lie to the public and enough fools will buy it hook, line and sinker such that the truth can be hidden.
IF Connally really was struck a split second AFTER the JFK head shot, then people would have heard BANG-BANG or words to that effect. Dozens described a bang, seconds of pause then BANG-BANG.
YOUTUBE Introduction to 0.7 Seconds to Conspiracy; Proving Conspiracy
In the video, I show a few of the witnesses who heard BANG-BANG (there are MANY more that I do not show here) but most importantly I show that what might be the best evidence in the JFK assassination was viciously attacked and discredited by the government friendly press. Probabilities PROVE that since the timing of the shots MATCHES in TWO independent ways to measure the timing of the shots PROVES that both methods show the correct shot timing.
After you understand this information is sufficient to prove the shot that hit JFK did NOT come from behind, then it is shown that the killer of JFK did NOT ride in this car! But even if you understand everything in this brief presentation, there is a >99% chance that you will NOT believe it could be true. The brainwashing of the public has been that good even though the lies are transparently false.