I think your question rather assumes that antisemitism is rational, that there are reasons somewhere out there that would explain it. This is just not the case. No form of racism is rational.
FWIW, White Nationalists also hate Blacks, Latinos, Native Americans, Asians, Roma, Leftists/Liberals, LGBT, Muslims, people with disabilities, and often Catholics.
But yes, most of the conspiracy theories they hold center around Jews. Jews running the banks. Jews controlling the media. The global Jewish conspiracy. The dual loyalty myth. Cultural subversion. Ethnic Infiltration. It just never stops.