If the conspiracy theories about JFK being assassinated a group of 2-3 gunman, depending on which version you believe, these hired assassins are terrible marksmen.

For as close as the car was, it wasn't that hard of a shot. The bullet traveled roughly 80 meters. I can easily hit that easily thay with no issues and so can anyone else who has basic training on firearm usage. I've even witnessed some 14 year old hit a target almost perfectly centered 100 meters away on the first shot on a moving target.

Oswald was a competent marksman when he was scored marines, but his abilities slowly declined and his scores became worse. I find it more convincing that Oswald's mid level marksman skills was responsible for the assassination of JFK than the 2-3 supposedly trained assassins who shot 4-5 shots and can't shoot worth a load of crap, especially the guy who was at the grassy knoll (along with the other overwhelming evidence that shows other gunman were never found).