The Rothschilds, like all the great Jewish banking families, were Sephardi Jews. The Jews that lived in Germany and Poland and would become the victims of the holocaust were all Ashkenasi Jews - two groups which had nothing in common. The Ashkenasi were impoverished, kept in ghettos and had almost no political clout whatsoever. They first arrived in Europe around the early 18th century, arriving in the Eastern parts, and spoke Yiddish. 
The Sephardis arrived several hundred years earlier via Spain. They spoke Laddish and all the great Jewish banking families are from this group - and that is entirely an accident of history. The Roman Catholic church prohibited Christians from charging each other interest on loans, Jews were not subject to this law - so these Sephardic Jews, particularly in Venice and Naples could get rich running banks that would give loans when other banks wouldn't - because they alone could charge interest.

The victims had nothing in common with the people blamed.