No. What you describe, I just call a "conspiracy" (assuming the action is harmful or illegal or .. eh, I think the word "shady" probably fits best).
I suppose the participants technically do also have a conspiracy theory, but I think it's inappropriate to call their direct knowledge that. The hypothesizing is usually by nonparticipants, and if they come up with a hypothesis with enough evidence to back it up such that their explanation becomes widely accepted in the mainstream, then they have a conspiracy theory.
(BTW, I know I already lost this argument decades ago. I lost the fight over the word "hacker" too. But that doesn't mean I can't grind this axe for the rest of my life! The word "theory" means something, or at least it did/should in my fantasy world.)