His impulsive actions are overblown in the grand scheme of things. Had he lived, Oswald strikes me as someone who would have denied the crime right up to the electric chair.
Yes, the Ruby killing of Oswald is bizarre and fascinating by any standard, but attempting to make it an organized conspiratorial event is perhaps the ultimate in ad hoc theorizing.
The choice of an erratic, red-flag character like Ruby in the first place ... the way Ruby spent his morning, even though Oswald was supposed to be moved much earlier ... Sheba in the car ... Ruby at Western Union minutes before the shooting ... some prearranged "signal" to alert Ruby the time was now ... a DPD participant to let him in the alley door ... the car horn "signal" ... all the things that could have gone wrong as Ruby approached Oswald ... relying on a single shot from a .38 ... Ruby lives to tell his tale, represented by flamboyant civil attorney Mel Belli.
Yep, sounds like a DPD/Mafia operation to me. Yep, no one could think of a tidier way to eliminate Oswald than THAT scenario. I love Santo Trafficante's answer at some hearing when asked "What if I told you Jack Ruby had Mafia connectiions?" Trafficante: "I'd say the Mafia needs a new personnel director." Me, too, Santo.
(By "ad hoc theorizing" I mean: You are stuck with the events as they actually occurred and thus must force-fit them into a conspiracy scenario even though no real-world conspiracy would have looked anything like that unless the conspirators were absolute idiots.)