Coming to the opposite conclusion leads to unpleasant thoughts about American politics, which are ultimately unprovable.
But I suspect that it was the time to aim effectively on a moving target after working the bolt that gave Gunny Hathcock the trouble.
Hipper.
The 1960s and 1970s subsequently gave us plenty of unpleasant conclusions about American politics. From Vietnam to Watergate to COINTELPRO to the work of the Church Committee, a lot of rocks were uprooted that revealed rather nasty things crawling underneath. There were plots to do false flag operations (Operation Northwoods) and plots to kill Castro. Hell, we nearly blew up the world a year before JFK was killed on the basis of poor military advice and bad intelligence that missed the fact that the Soviets had tactical nukes to greet an invasion and submarines with nuclear torpedoes. Bob McNamara and his crew at Defense, the "best and brightest" of their generation, completely misread Southeast Asia and led us into a disastrous war in Vietnam. The government that led us out of the Depression and to victory in two world wars was shown to be imperfect, capable of great error and also capable of doing bad things. It was a disillusioning time and the assassination played into that; the vaunted Secret Service, the best of the best, couldn't keep a President alive on a simple motorcade through an American city.
But in the end, in the middle of the tumultuous events of the 1960s, people still have trouble grasping the idea that a very pathetic 24 year old nobody armed with a $12 rifle could change the world. It was an event of almost complete randomness: Oswald's job at the Depository, the route of the motorcade, the timing of everything giving Oswald the opportunity to be alone at that sixth floor window during lunch. People find that more disturbing than the idea that the CIA, the Mafia, LBJ, the FBI, or any other people or organizations planned and carried out an assassination. Senselessness and randomness is always more distressing than slick plots and conspiracies, for with the latter there is the hope of controlling dark forces. With the former, people are frightened by random events which lie beyond the realm of human control.