Two elements all good successful conspiracies must have, a plan and executors smart enough to pull it off, and ultimate secrecy. Both together, with numbers of people involved, realistically sinks most theories potential before they even leave the gate. It's a lot easier for just one person to lie, after the fact, to bend reality/perception as desired.
Reality check, that half the population is smarter then 50% of the people and it's a constantly contested fact.
