That said conspiracy theories are based around areas where a complete knowledge is not available. The description of the problem maybe correct, but the motivations of the parties involved wrong. To discredit an idea simply because it is a conspiracy theory is illogical.
Many popular conspiracy theories involve huge numbers of conspirators - thousands, or even hundreds of thousands. For anyone who has a "feel" for how math works, it seems wrong. Putting some hard statistics work around it makes the false nature of large-scale conspiracies more concrete for those of us who believe in math.
A conspiracy theory where no more than a dozen people need to be involved makes sense to me. A conspiracy theory involving every climate scientist in the world, or every doctor in the world, or every NASA employee, seems like BS.
There could be informal conspiracy, take the 2008 financial crisis. Everyone was working in their own self-interest, and there were thousands of them doing it. From the outside it could look like they were working together to some nefarious ends.