Because the sine qua non of Naziism is antisemitism of a particularly virulent type. One could imagine a Jewish white supremacist, but that's not the same as a

Because the sine qua non of Naziism is antisemitism of a particularly virulent type. One could imagine a Jewish white supremacist, but that's not the same as a Nazi. A Jew, for obvious reasons, isn't going to be an antisemite let alone a particularly virulent one.