The President happened to drive by the place where Oswald worked. Had he not, you would never have heard of Oswald.
A lot of things have to come in to play for most things to happen. When they don't, they don't happen, and nobody is aware of what might have happened.
The top being removed from the car and security removed at the last minute are biggest clues to a conspiracy
Security wasn't removed. The top was removed because the sun was out. It was only used to protect from rain, and wasn't bullet proof.
“Security wasn’t removed.”
This is one of many places I’ve heard otherwise....
http://www.jfklancer.com/LNE/limo.html