It seems now and days theres a lot of conspiracies or running gags that jews are behind a majority of man made disasters, they run the world, or something that happened was the jews in the banks.
Where and why did these accusations, along with the running gags come into fruition? Is it based off of racial issues and stereotypes or something completely different?
I have a related question. I was recently reading some historical fiction from the middle ages and in it it is said that the reason the people borrow money from Jews is because Christians can't charge interest.
Is this accurate? And if so, where did that idea come from?
Hopefully someone can offer a more substantive answer to your question, but as for modern notions of Jews running the world or banks, look to The Protocols of the Elders of Zion, a very well known piece of propaganda that came out of Russia in the early 20th century. Anti-semitism of course predates its publication, but this is the earliest piece of writing I know of that proposes a world wide conspiracy of Jews who control society at large.
If you haven't already seen it, there is a substantial section of this subreddit's FAQ devoted to questions similar to this.
I don't think that the specific topic of global conspiracy has a dedicated question in the list, but as mentioned by /u/delosas elsewhere in this thread, the Jewish contribution to the history of the finance industry is pretty well documented. It's not a hard leap to assume that anyone with money exerts some degree of political influence (as the finance industry as a whole is frequently viewed today). Conspiracy theories frequently use a visible person or group to invent a narrative around, and Jews are just another entry in the list of the arbitrarily villainized.