It is not a lie. It is tribally epistemic. And is obedience centric. Obedience to the tribe is driving the theory far more than anything else. Especially the literal truth.
So a conspiracy theory, is signaling truth, in myth and symbol, because that is the only way to signal it. It cannot be done literally for various highly rational reasons.
Several primary reasons might be:
1) by speaking it too literally may see you sent into exile by the tribe because it is forbidden language and knowledge
2) by speaking it too literally you may surreptitiously be found complicit in the very problem you're signalling
3) by speaking it too literally might place you in a position of significant shame and guilt
Whatever the reason is for any particular theory, there is always danger involved, usually in the form of a serious threat by the tribe(collective or constituency).
And this danger is the reason these truths, which are real, can only be told by way of a conspiracy theory, because that action helps the speaker escape from the danger in it.
Sure, one might be regarded as a nut job for telling the theory in myth and symbol, in public. Surely that is better than losing your job, house, family or even your life?
A Conspiracy Theory, is a Truth, Which Cannot Be Told in Any Other Way.