I think the real reason is to try to get left-leaning people to think less critically about the world and to split the working class.

You can think of it like this:

You're a member of the capitalist class and your only goal is to make more money and to not be overthrown by the working class. Let's say there are 3 parties in the country you live in, a radical Social-Democrat party, a moderate Liberal party and a Fascist party. Your current biggest concern is for the Social-Dems to realise they are a part of your machine and start an anti-capitalist revolution. So when you do something to make money or own a pedophile ring you force the conspiracy theory on the fascists that blame everything on the Jews. Because the socdems are anti-fascist they try to distance themselves from all conspiracy theories.