It seems odd that the Nazis targeted Jews, a group that essentially look exactly like Europeans, over say Africans, Muslims or Asians. Was it the religious aspect as well? Even then, African, Muslim and Asian religions were even further from Christianity than Judaism.
There's always more to be said, but /u/yodatsracist explains the history of Jewish people being targeted in Europe in this excellent post, while /u/kieslowskifan in this post clearly explains here how the particularly German version of anti-Semitism developed and then became the anti-Semitism of the Nazis.