Three can keep a secret, if two be dead. And if I thought my hat knew my counsel I would cast it into the fire.
If a theory relies on there being a conspiracy, then that is a priori a very high burden on it. Conspiracies are hard and unstable.
Some social structures can evolve that allow secrets to be kept with larger numbers of people. For example, intelligence agencies are not only compartmentalized, but the employees making them up all assume that if someone approaches them offering to buy secrets, that it’s probably one of the routine counterintelligence operation within the agency that draws out and prosecutes untrustworthy employees. As a result, the employees basically two-box their agency and never accept bribes from foreign agents, no matter how large the payout. And any that fall through the cracks are hard to disentangle from disinformation by double/triple agents posing as easily-bribed-people.
It’s much more complex than that, but that’s just one example of a secret-keeping system evolving inside institutions, effective enough not just to keep secrets, but to thwart or misinform outside agents intelligently trying to rupture secret-keeping networks (emerging almost a hundred years ago or earlier).
Some social structures can evolve that allow secrets to be kept with larger numbers of people. For example, intelligence agencies are not only compartmentalized, but the employees making them up all assume that if someone approaches them offering to buy secrets, that it’s probably one of the routine counterintelligence operation within the agency that draws out and prosecutes untrustworthy employees. As a result, the employees basically two-box their agency and never accept bribes from foreign agents, no matter how large the payout. And any that fall through the cracks are hard to disentangle from disinformation by double/triple agents posing as easily-bribed-people.
It’s much more complex than that, but that’s just one example of a secret-keeping system evolving inside institutions, effective enough not just to keep secrets, but to thwart or misinform outside agents intelligently trying to rupture secret-keeping networks (emerging almost a hundred years ago or earlier).