I would submit that the Jewishness of the Rothschilds is essentially unimportant, a red herring to keep everyone off the trail. But how could anyone think that?

The Rothschilds were just some nobody Heebs living in the Jewish ghetto of Frankfurt, but then we find this in the wiki of the progenitor, Mayer Amschel Rothschild:

With the help of relatives, Rothschild secured an apprenticeship under Jacob Wolf Oppenheimer at the banking firm of Simon Wolf Oppenheimer in Hanover in 1757. The grandson of Samuel Oppenheimer taught Rothschild useful knowledge in foreign trade and currency exchange, before he returned to his brothers' business in Frankfurt in 1763.

He became a dealer in rare coins and won the patronage of Crown Prince Wilhelm of Hesse (who had also earlier patronised his father), gaining the title of "Court Factor" in 1769. Rothschild's coin business grew to include a number of princely patrons, and then expanded through the provision of banking services to Crown Prince Wilhelm, who became Wilhelm IX, Landgrave of Hesse-Kassel in 1785. Business expanded rapidly following the French Revolution when Rothschild handled payments from Britain for the hire of Hessian mercenaries.

By the early years of the 19th century, Rothschild had consolidated his position as principal international banker to Wilhelm IX and began to issue his own international loans, borrowing capital from the Landgrave.

I suggest the key lies in Frankfurt, although exact names still elude me. To wrap it back around, Samuel Oppenheimer was born in Heidelberg, less than 50 mi south of Frankfurt.