It occurred to me that whichever outfit killed him could then have caused yet another power struggle. Lining up the next lot of dominoes to fall. If the top man goes to the place he benefits from, after JFK is gone, you get a power vacuum at the top I think. Maybe that is why there were the deaths of so many unsavoury characters, falling out with each other both within their organisation and with their rivals. A bit like Spy V Spy in MAD magazine. Add in potential blackmailers and downright liars to the mix. Could this be part of so many linked deaths ?.
I don't know if you heard of the London gang leaders the Kray Twins. One walked into a pub, the Blind Beggar, and shot a man dead. If all the people who claim to have been there actually were there it would 'fill a stadium'. That pub is tiny.
I think the documentary I saw, which lined up Ruby to shoot Oswald dead, and showed all the steps so clearly, makes most sense to me. BUT I still have no idea who really fired the shots. Umbrella Man was signalling to somebody !