The anti-semitic idea odf the Jew as a greedy moneylender or banker is much older than nazism as an ideology.

The catholic church considered interest usury and a sin until the 16th Century. Before the reformation, christians were not allowed to charge interest, which severely limited the ability of christians to lend Money or have banks as a business.

However, jews were not limited in the same way - their religious rules allowed them to charge interest from gentiles (ie non-jews). Jews were also forbinned to own land and often barred from the craftsmens' and traders' Guilds in the towns and cities - thus one of the few professions that were open to them were moneylending and banking.

When the catholic church started to open up to to the idea that interest was not usury after the Fifth Lateran Council in 1515, and the new protestant faith had no problems with interest, there had ben jewish bankers and moneylenders for hundreds of years in Europe. Having sucha head start meant that they continued to be prominent bankers. Jews had also often been hired as chancellors, tax collectors, finance ministers (such as the role was back then) and other administrative roles around money due to their and their families experience with the subject.

The secret servicer of the Czar of Russia created fake protocols of a jewish world organisation which showed a international jewish conspiracy aiming at world domination. Protocol 20 specifically deals with how jewish bankers are to use thier influence over the world economy to dominate the gentiles. The forgery was first published in 1903, but reached worldwide spread despite being proved as a forgery by The Times as early as 1921. The nazis studied these documents throroughly and made them required Reading in school when they assumed Power.

World war 1 was a war fought extensively on credit, and of course some prominent bankers, some of which were jews, benefitted from this. The economic turmoil of the great German inflation and the great depression made people look for scapegoats and bankers were blamed, and jewish bankers especially.

He would also have picked up general cultural background noise of anti-semitism which was widespread and common throughout Europe.

A brief list

Shakespeare: The Merchant of Venice

Marlow: The Jew Of Malta

Ivanhoe by Sir Walter Scott

Dickens with Fagin in Oliver Twist

Wagner in his essays and Ring Cycle

All the above portray Jews as being amoral and money obsessed.

So by Hitler's own time the perfidious myth was so accepted by the mass of people as to a 'fact' of the 'everyone knows that' variety.

A good example from Hitler's own time from Modernist literature forms one of the principle themes of James Joyce's Ulysses (written between 1914 and 1921 and set in 1904) highlighting the rampant anti-semitism that was pervasive at the time

In Chapter 2 'Nestor' the Headmaster Mr Deasy is giving an unasked for lecture to the book's second protagonist Stephan Dedalus

"-Mark my words, Mr Dedalus, he said. England is in the hands of the jews. In all the highest places: her finance, her press. And they are the signs of a nations decay. Wherever they gather they eat up the nations' vital strength. I have seen it coming these years. As sure as we are standing here the jew merchant are already at their work of destruction. Old England is dying."

The other protagonist, the Jewish Leopold Bloom faces all manner of unjustified snide remarks and cruel unfounded comments about his supposed parsimony and 'cuteness' with money

So sadly the ideas were 'low hanging fruit'

"In the early nineteenth century, thirty of the fifty-two private banks in Berlin were owned by Jewish families; a hundred years later many of these banks became shareholding companies with Jewish managers, some of them directly related to the original owners as well as to each other. The greatest German joint stock banks, including the Deutsche Bank and Dresdner Bank, were founded with the participation of Jewish financiers, as were the Rothschilds' Creditanstalt in Austria and the Pereires' Credit Mobilier in France. (Of the remaining private-i.e., non-joint stock-banks in Weimar Germany, almost half were owned by Jewish families)"

From page 47 of Yuri Slezkine's "The Jewish Century"