Also; who profits?
Consider what happened to LBJ(a jerk and a true FDR democrat) after JFK (not the dove he's portrayed to be) was disappeared ?
The left ate Johnson alive and made sure he was broken away from the Kennedy myth.
The democrat party turned totally away from anything Truman or JFK would have supported and led us steadily to the fecal repository (can) we find in today's DC.
LBJ was probably too canny to have a national level opponent burned on his (Texas) turf.
In '63 I watched the coverage (from college - I was a liberal then...'till drafted) and heard/read all the after reportage, I heard it all again ten years later on tape, read the theories and collect WW2 rifles, and I have no hard opinion on who or where the shots came from ('though the grassy knoll DID stand out in all those real time reports) so I can't add anything to the specific shooter debate.
But I do seriously believe that the hit was bought and paid for by someone within the party who had a vision of the direction history was fated to go - and now we're almost there.