Is it possible that a small and secret although powerful group somehow manipulates global society and directs the course of history? No. All the evils supposedly explained by the conspiracy are fully explicable by economic processes and social interactions that anyone can study. Patet Veritas Omnibus ("Truth lies open to all" - the motto of Lancaster University).
If there were any such conspirators, then how would they do it? Economic and financial powers (i) are very great, (ii) can be centralized in very few hands and (iii) can be exercised by people who keep their names and faces out of the news. I think that the conspiracy theory is a "fantastic reflection" of the real world.
(i) In Poul Anderson's "Details" and "No Truce With Kings," two different sets of aliens concealed among us apply a superior social science in order to manipulate humanity - but fail.
(ii) Anderson's psychotechnicians advise governments but also operate secretly and dishonestly and are overthrown as a result.
(iii) Isaac Asimov's Second Foundationers apply a predictive science of society and also deploy fantastic mental powers.
According to Jerry Pournelle's and SM Stirling's "The Asteroid Queen," Marx, Charlemagne, Hitler and Brennan (the Belter who became a protector) were all members of the same ancient, secret, world-controlling Brotherhood. Not in our timeline! And maybe not in the Known Space timeline either? The Brotherhood suppresses knowledge and propagates:
"...slanted versions of past, present, and future." (Man-Kzin Wars V, p. 26) -
- so maybe it lies to itself about its own past?
-copied from here.
To show how imagination that could be invested in the writing of fiction is instead deployed to devise complicated conspiracy theories, let me quote some of what I heard last night:
the City of London controls the world financially;
the City of Washington controls the world militarily;
the City of Rome controls the world religiously;
behind the public "White Pope" is a "Black Pope," the head of the Jesuits;
behind the "Black Pope" is a "Grey Pope" who is - who or what exactly?
How does the Grey coerce or control the Black? How does the Black coerce the White? How does the White oversee anything but the beliefs of his co-religionists? (Is it possible that the term "Black Pope" has been used jocularly? - but no more than that.)
When I expressed skepticism about the Grey Pope, I was advised to do my research so I googled and read some nonsense which was cheek by jowl with vile propaganda. I think that, in this milieu, "research" means reading books or websites which merely state that there is a conspiracy.