Conspiracy theories are 'sour grapes' rationalizations: ways of justifying and excusing the failures of a belief system. At the heart of every conspiracy theory is an ideology or set of beliefs that did not work out as planned: what should have happened (according to the belief system) didn't; what did happen (according to the belief system) should have been impossible. But instead of questioning, examining, revising, or discarding this belief system, the conspiracy theorist asserts that the belief system failed to have its expected outcome because vast networks of people joined in conspiracy to undermine and subvert the 'natural' and 'correct' order of things.
Conspiracy theories are always present within the more self-righteous, dogmatic elements of any belief system (Left, Right, or Center), because individuals who are prone to self-righteous, dogmatic thinking often have difficulty accepting the failure of their efforts. Anyone who truly believes they have found the 'correct' way of understanding the world will have difficulty accepting that this ostensibly 'correct' understanding does not yield immediate and tangible results, and it is often easier for such people to embrace improbable explanations for that failure than to do the mental work of revising their beliefs. Belief systems create existential security. For those who are deeply egoically attached to their belief systems, any perceived weakness in that system can produce levels of existential angst that are incapable of facing directly.
Over the last three or four decades, the conservative movement in the US has seen repeated losses and failures. Social policy has become increasingly liberal and secular; fiscal policy and regulations have become progressively federal and 'Big Government'; corporations have displaced the political and social power of individuals; minorities and women in US have made notable advances into the traditional white male hegemony. Every time a Democratic administration comes to power the wealth and status of the nation rise, while every time a GOP administration comes to power the economy and US reputation collapse. The further reaches of the Right in the US can't ignore these failures that seems directly connected to GOP/conservative belief systems, but they cannot emotionally accept that there are flaws within the belief system itself. So they turn to ever more extreme and wild theories to explain why they have failed to achieve their ideological goals, imagining that cabals of people are secretly and nefariously subverting the system, and thus subverting the natural order in which their ideology would unquestionably be successful.
Sometimes there are conspiracies, no question. As the old saying goes, being paranoid doesn't mean people aren't out to get you. But by the same token, having people out to get you doesn't mean you're not paranoid. Society and politics are competitive institutions, and sometimes when you lose it's right and proper that you lose.