I guess this is the right place because it's more to do with why people believe conspiracy theories, than discussion about an individual theory.
Most people believe conspiracy theories and at the same time criticize all religion and call it utter rubbish. Though there isn't much more proof for some conspiracy theories than there is for religion.
I think for people it's easier to think that humans aren't naturally capable of "evil" and are in fact influenced by lizards or who ever else into being evil, than it is to except that human nature contains good and evil.
Also if people think that humans are manipulated into being evil by outside sources it gives them hope that humanity could unite to over throw these evil oppressors, and that from then on human nature would only ever be naturally good and pure.
If people except human nature is naturally capable of good and evil then they have to accept humans always will be, and always have been this way. Then that will remove in there mind the chance of saving humanity and bringing it in to a golden age of all love and kindness and zero negativity.
It seems in this way conspiracy theories are very similar to religion in that they act as a crutch to fend off the bad aspects of the world and human nature. Another similarity is the belief that with out the negative influence of "evil" be it from the "devil" or "lizards" then human nature would be good and pure.
We all know humans are capable of good and bad. We have always been this way, and always will be. Society's change, but people don't. You get different configurations of people with certain aspects of their nature spread out differently in other societies, and with certain personality types more prevalent in other societies. Though human nature is still the same as it was in any other society, even post society and agriculture human nature was the same.