Well, they didn't like his artwork. That is true, but seriously, I think it was easy to use the Jews as scapegoats because Europe - not only Nazi Germany - had been using them as scapegoats long before the Third Reich.
Jews were blamed for spreading the Bubonic Plague in the fourteenth century. In 1492 Colombus sailed the Ocean Blue - and Spain expelled the Jew. The Church had long suspected Jews of drinking the blood of Christians as part of a blood ritual. Martin Luther, the good German and Mr. Protestant Reformation himself, was incredibly anti-Semitic. So I think it was easy for Hitler to use them as scapegoats since there was already an atmosphere of anti-Semitism prevalent throughout Europe - not just in Germany. And Hitler used more than simply the Jews as scapegoats - gypsies, homosexuals, socialists, the mentally ill - anyone who wasn't a pure, healthy German he considered a threat to Aryan purity. And used that insane logic to justify (or attempt to justify) the necessity of war.