I think I would look to history for an explanation of each individual "irrational" belief, rather than to an underlying unified theory of 'why people believe patently false things." for example,That Finance is controlled by Jews is an idea with a very ancient history of connecting jews with money and greed. Judas sold Christ for gold, Christ drove the moneychangers out of the Temple. Antisemitism, as Elaine Pagels shows, was part of the process of defining Christianity as not a jewish sect: the Gospels consistently move chronologically toward making Jews villains in the christ story: the earlier Gospels emphasize the roman role, the later ones the jewish mob calling for jesus's execution. Later, jews were connected with the devil, black magic and of course with "usury," which Christians were not allowed to practice and regarded as evil. Barred from owning land or farming it in many places, they gravitated toward cities, trade, storekeeping, knowledge-based professions -- modernity.
Similarly, That Jews are an "international" cabal, not "really" members of the communities and nations and people "among whom they live," is very old also, and still has a lot of life in it. (cf. gore vidal accusing American Jews of being a 'fifth column" supporting Israeli over US interests -- he would never call other US ethnicities traitorous for advocating particular foreign policies, no matter how ill-advised those policies were.) Anti-semitism is one of the features that ethnically-based and/or Christianity-based nations define themselves by means of -- that's one reason there can be anti-semitism without jews, as in modern Poland, or for that matter, much of the US.
Without Christianity, I don't think anti-semitism would exist.The origins of the belief that immigrants will "steal" your job are different.
Katha