My husband agrees it was an easy shot but I still think that Oswald did not come up with the plan all by himself. He may or may not have been a lone gunman. He had others helping him. Whether it was LBJ or the Mafia or Castro or someone completely unknown, someone set it up for him and then Jack Ruby to wipe out Oswald so he could never tell.
I see it as a spur of the moment event. Oswald saw JFK was coming to Dallas and the route had been published in the paper several days prior and the route took the motorcade right in front of his workplace on Elm Street. Some claim the Elm street turn was never published but that is because one paper did not publish the updated route and they quote that paper. However, several other papers, including one in Houston published the correct route as early as two days prior. Oswald was a nut that went so far as to travel to Russia and the Russian embassy in Mexico to offer his services as a spy or agent. He stood on street corners passing out pro-communist literature even after being harassed for it. He was a nut that wanted desperately to gain the attention of the Soviets. It was the height of the Cold War and he wanted to be in the limelight, not understanding that spies operate in the shadows and not in the limelight. I see perfectly that he jumped at the chance to shoot JFK that day. He didn't know if his plan would succeed. He didn't know if he would ever get the chance. He didn't even have an escape plan, or even a plan to dispose of his rifle; he left that behind some boxes. I don't think he thought for a second that he could just walk out of that building so easily. He hastily left, and due to the incompetence of the cops he was able to.
Here's a image of the Boston scene whereby the suspects had a shootout with these guys and...left. Weren't found until a citizen found one hours later.
Every time the movie, “JFK”, is on TV I try to watch it. Kevin Costner stars in it. Interesting and a little bizarre. Each time I see it, I catch something new.