This is my theory as to why "conspiracy theories" exist. This cognitive disturbance happens because people are brainwashed to think a particular idealogy is good, while another is bad. However they observe the opposite in their day to day lives. To reconcile the disconnect between what they think they know and the way reality actually works an elaborate theory is constructed.
Since socialism is bad, then socialism must have secretly taken over capitalism, which is good. Voila! a conspiracy theory is born.