Well Pat, if you go carefree down that road (or rabbit-hole) it has no end.
Why not impossible -
Kennedy lost the election but the count was rigged and he was never president?
Kennedy was rubbed out 6 months before and it was a double that was shot?
the Russians gave Castro the Kennedy contract, and he hired the Mafia who passed it on to the CIA who gave the job to a sleeper who did the shooting and they framed Oswald?
Tomorton, if you are looking for motives, there is no bigger motive than money and national interest.
Government contracts are in billions. For all we know it was one small company that gained to make $5m dollars.
Irrespective of whatever, you have to carry out a basic test. Given your age I'd guess you fired guns in your life time.
So if it takes able marksman 19 seconds to load and fire three rounds in that bolt action rifle, shouldn't you be asking where the 9 seconds came from for Oswald to aim and hit a moving melon in a car from 80 yards? . He must be one hell of a super hero. Even in their testimonies they refer to a magic bullet. LOL... Some magic bullet indeed.
As far as I know back then and now, security and police forces always have connections with the underworld. Not beyond imagination. Just reality imo.