Assassination researchers are almost all from the "JFK was killed because he was good" school. Now, they all have different goodnesses in mind (Vietnam, Federal Reserve, civil rights, anti-mafia, etc, etc, etc).
In real homicides, the victim is often killed not because they are good, but because they are mixed up in something bad.
Of this, there is abundant evidence in the life of JFK.
I am fascinated by the case, and I think motive is the key to the solution.
I will suggest a motive or two:
LBJ - Power. He was relentless in his quest for power and control and was willing to use any means. JFK would have served eight years and Robert eight after that. By then, it would have been too late for LBJ. He was also a buddy of J. Edgar Hoover with them often sharing whiskey late into the night and regaling each other with seccrets about other politicians, including the Kennedys. Robert, as Attorney General had little respect for Hoover and, as his boss, ordered him around.
The Mafia - After assuring his election by stealing votes in Chicago they felt JFK owed them something. Instead Robert went afer them hammer and tong.
Mafia, LBJ, FBI - The word on the street about Robert was "Kill the head (JFK) and the body (RFK) will die" in concern about Robert's pursuit of the Mafia. Further support for their mutual interests was the death of Robert after he won the Democrat primary in CA in 1954 and said, "Now on to Chicago." He was then a real threat to them all.
Now there is your motive. Did that lead to the deaths of the Kennedys? I report, you decide.