Jewish people are often associated with business and trade. I do not get the sense that Jewish people in the old testament were associated with trade and business to an unusual degree, so at what point did this association begin? I know during the high middle ages, Jewish people played prominent roles as entrepreneurs and moneylenders. Would they have played such a role during the late roman period? How about during the era of the Roman Empire?
According to Islam, it is immoral to handle currency, like in a bank. This discouraged or outright made illegal the position of banker or loaner. Because of this, the job fell on the Jewish people.