As a nephew of someone who happened to be a very close associate of Lyndon Baines Johnson, this is my take on the whole thing. John and his brother Robert were allegedly involved in Marilyn Monroe's death, and LBJ used this "fact" to garner overwhelming support in favor of Kennedy's assassination. His true intentions however were most likely that he wanted to make sure that he [1] was not implicated in the "Billy Sol affair" and [2] could become president. Incidentally, if it were not for the fact that Hoover had been pulled into the scheme, Oswald might have gone down in history as a hero. Why? Because he was reporting the progress of the "plans on the ground" to the FBI on a regular basis. Unfortunately for him, Hoover was burying these reports, just as Oswald himself was being designated as the most convenient fall guy. In truth, I believe that he was a patriotic (if naive) "agency man" who gathered much useful intelligence for US interests, including a detailed report concerning operational matters relating to an electronics factory in Minsk, key Cuban assets, and of course details about a plan to take the president's life! It's a very sad twist of fate, but it just goes to show how cronyism can tarnish even the most prestigious institutions. As for official recognition of "the truth", that will probably never happen. It would only open a can of worms that nobody wants to deal with...
You have to remember that Monroe was considered a "national treasure" at the time. Her death was a huge shock to pretty much everyone, and any evidence tying the Kennedy's to her death (and LBJ ostensibly had a recording of it) would have been an "ace in the hole" for anyone trying to plan JFK's murder. Members of the so-called "Suite 8F Group" such as D.H. Byrd (who also happened to own the Texas School Book Depository) could have been easily swayed by such "facts". And keep in mind that these men were already not very happy about proposed changes to "oil depletion allowance", among other things.
if jfk and is bro were guilty in marilyn's death then you could only blackmail those who don't want any harm to come upon jfk ... why would those people collaborate killing jfk then?
if jfk and his brother were guilty in marilyn's death then you could blackmail them. having a president who is susceptible to blackmail is a threat to the country. killing jfk would remove that threat.
Okay but then it would be the Soviets who had detailed information on JFK murdering her, and that was being actively used as leverage against JFK. Then it would make more logical sense for the US government/CIA to remove JFK. The movie script here needs to get updated to make it a bit more plausible. Make it so that the USSR was blackmailing him to pull out Vietnam or something.
I have a good one too, but it's totally bupkiss. Nonetheless, it's a fun one.
Joe DiMaggio had JFK killed.
DiMaggio's family hails from Sicily and had a lot of mob connections in the East Bay. JFK was famously barred by Joe from attending Marilyn's funeral, due to his jealousy and implications he held that JFK was responsible in part for her death. Via mob connections and his time playing with/against Ted Williams, Joe manages to get Oswald, a Marine like Williams, to do the deed.
I haven't researched the subject in years, but perhaps you could start with the death of Henry Marshall at the USDA? The information he was gathering was related to the business schemes of Estes, Johnson, Clint Murchison (Sr), and others. (Estes was eventually sent to federal prison over related charges, but the investigation basically stopped there.) From Wikipedia:
"In 1962, after information came to light that Estes had paid off four Agriculture officials for grain storage contracts, President John F. Kennedy ordered the Justice Department and FBI to open investigations into Estes' activities and determine if Secretary of Agriculture Orville L. Freeman had also been compromised (Freeman was cleared). Congress conducted hearings on Estes' business dealings, including some that led to Vice President Johnson, a long-time associate of Estes."
Just a reminder that someone claiming to be the nephew of an "associate" of a historical figure, with extraordinary claims and zero evidence, is not a very good source.
Take it as you will. It's nothing more than anecdotal hearsay, naturally. But it doesn't take a lot of digging either to find that it jives with the much of what has been revealed over the decades.