I don't really know a lot about JFK conspiracy theories. Does anyone here think his assassination was a government conspiracy? If so, who did it and why?
I've studied the assassination at length. There was definitely a cover-up, but as for if the government did it, it's still speculation.
The level at which it was executed and covered up, the CIA is the #1 suspect. The CIA was going to be disbanded by JFK, so this puts more believability in their involvement. It's believed that they teamed up with the Mafia to accomplish this and tie up the loose ends.
Next, Cuban communists/KGB are also considered. Because of Kennedy's victory in the Cuban Missile Crisis, they plotted their revenge. Once the CIA and FBI discovered their involvement, they covered it up to prevent public outcry for another war, with them already in Vietnam their resources would be spread much thinner.
The last most plausible suspect is simply the Military Industrial Complex. It's no surprise that they thrive on war, and with JFK's plan to pull out of Vietnam, and the obvious reversal of his plan when Johnson showed up, it raises some red flags.
As for my opinion, out of all the books I own, videos I've seen and evidence (that cool magic bullet that the Warren Commission tried to sell the US citizens) on the subject...I believe it was a mix of the MIC and CIA.