In terms of Hitler/ Nazi Europe/ WWII/ Holocaust?......
The Jews were a religious/ occasionally ethnic minority in Europe making up 1%-13% of the population depending on country. Originally an advanced people of the Middle East and ancient Roman world they were clannish to preserve their identity, very talented at business, banking, arithmetic, science, arts, crafts, unarmed and non fighting/ non war like, many were also wealthy.
In European history Jews were often hated for the traits listed above and especially for being wealthy, and talented in business and crafts. When something went wrong in European history the Jews were often blamed wrongly as scapegoats for whatever had gone wrong. They were then a target to be mistreated and looted of wealth. Germany in history had a particularly bad record in mistreating Jews and all minorities.
Hitler and his Nazis were extremely violent nationalistic, extremists, fanatics, racists who worshipped evil, war, power, violence, cruelty, and genocide as a 'new world order'. Having gained power by terrorizing the German public, they had to unite the public behind a target to aim the evil, violence, cruelty, racism they created at. They picked the Jews as the logical target. This time Nazis being extreme fanatics/ extremists after looting the Jews of all and torturing them decided to genocide them all (that is murdering every Jew in Europe and then the world). The Nazis had plans to do this to many other peoples too. They succeeded in murdering by torture/ mistreatment 2/3 of all European Jews in the 'Holocaust'.
Hitler and the Nazis hated Jews (and the others) to that....so much degree.... of genocide of whole peoples by torture, because he and they were so extreme/ fanatic/ sadistic insane and evil, they became what they worshipped and believed.