I've been thinking about the Kennedy assassination, then the Tate-LaBianca murders, two epoch ending events, whose effect was the end of liberal governance (ok, that's overstating it a bit, the last liberal President was Nixon--as Chomsky says, but that might only have been the assassination aftermath corrected the rightward bias of the assassination itself), the the end of liberal culture. My thinking is that there were likely inputs from many sources alleged by conspiratorialists (of whom you could say I was one). For example, had the CIA not had the MK ULTRA program, and not experimented with LSD, the Manson murders could not have occurred as they did.
Did CIA/FBI/Mafia/KnightsOfMalta/dissaffected-nationals/Hoover direct the outcome more tightly than that, perhaps suggesting or listing Tate (such as hit one of these, and we'll let you live)? Well that's into conspiracy territory, no evidence exists, but then none would be expected. Remember the tape recorder on Mission Impossible. Only a small group of people might have ever known. But then, perhaps through some screw up, the table was tilted, as these programs certainly involved people with far right and racist views, like J Edgar Hoover himself, a finite number of people could have been targets, planned or unplanned. Then where would you put the matter if CIA/FBI had a pot of money for this kind of thing, embarrassing Black power movements, but simply left the who question to the perpetrators, who would understand the biases of their clients? They would have chosen 'someone like Tate' (a left liberal movie icon) as to not offend their clients and someone they could get their hands on, and not someone of other persuasions.
Anyway, determining most important or proximate causes may be more difficult than one would naiively suppose, especially in the broadest view, when you can consider counterfactuals of all kinds.
For example, what would have happened in the truck had broken down on the way to the Tate residence? Well then the murder wouldn't have happened that night anyway, and Manson might have had a different goal the next day, if any.
Then where do you put such things as the highway itself. Or the invention of things like automobiles. Surely without those, both of these events cound not have been anything like they were.
When it comes right down to it, the cause of everything is everything.
So where does that leave us? Causality cannot be considered an absolute description of everything that happened. Only a description of everything that happened can be that, or some description of the same scale. Causality is a story we create about events, selecting which things are the variables and which things are the fixed. But the reality is that all are variable, it is only in our mind we consider some things part of a fixed background, which is the context which must exist for a notion of causality.
BTW, if you read over on my other blog, I have a (likely untrue--falsely remembered from misplaced details) story in which I caused the Tate-LaBianca murders by insulting Manson's drug access compared with that of my chosen (Hollywood) people.* So he murders a couple of Hollywood dealers and their favorite clients to put me in my place (fear if not respect of him). The LaBianca portion of the murders were related to my mother's first name, literally "La Nore" (she insisted on the space), so it was some kind of coded message (watch out, kid, you might be next).
Now what if the Manson murders had actually been sparked by some 13 year old kid's insult at a park? Consider the extreme case in which there was nothing else, particularly, behind Manson's decision to order murder at all AND to order murder for these specific people? In what sense would you say that I caused the murders? Well it certainly wouldn't be a matter of criminal liability on my part. I had freedom of speech and an inherent right to defend myself by insulting a creepy guy. I did nothing wrong, or at least nothing illegal. Certainly a kid's insult isn't in any kind of balance with a terrible murder. But from a neutral standpoint, not related to social judgement, I was part of the causality, and a more active part than a molecule in the roadway between Spahn Ranch and Cielo Drive (which must have taken a bit longer than the 20 minutes I've seen quoted)--which would have been nevertheless "a part" of the events that actually took place.
And so, guilt is restricted form of causality, a more particular kind of story. When assessing guilt, we leave out a universe of additional causative factors, to focus on those assumed to be part of human free will.
*When I met Manson at the Chatsworth Park--2 miles from Spahn Ranch--during the years 1967-1969 preceding the Tate-LaBianca murders, possibly only days or hours beforehand, he first struck me as a country bumpkin Christian promoting his church. Though I was only a 13 year old kid who had never used drugs, it struck me that I did not want to be leaving my infinite LA culture and becoming Christian in some country bumpkin church because that would mean giving up on a lifetime of playing with psychedelic drugs, as I imagined my future. When we first started talking, he pointed out some alleged gaps in my world view, making me angry because I couldn't see through his rhetorical tricks. I retorted something like "But you don't have any good drugs. What fun is that?" All the Christians I knew were opposed to drugs. If this is an accurate recollection--and I have serious doubts--the irony is incredibly thick. I recall Manson quickly blurted out a bunch of details proving he knew plenty about drugs as he walked away. I was a little blond headed kid, and my best friend and guide was a brown haired jew who had begun styling himself to look like Roman Polansky--in part because Rosemary's Baby had been his favorite movie. All this could have made Manson angry, and angry specifically against blonde and jew pairs. We might have been a causative factor, but not a guilty one.