Is that important?
I have a certain affection for David Scheim's book Contract on America: The Mafia Murder of John F.Kennedy which goes into intricate detial about who might have wanted to kill JFK, what their friends and accquainatnces thought, while ommitting all mention of what actually happened in Dealy Plaza on the day.
Of course it’s important. If motive is your only proof, Dealy Plaza would have sounded like D-Day.
In order to prove who killed someone, you have to know who pulled the trigger. A fact no conspiracy theorist can explain.