The simplest answer is "scape-goating".
But that's not really a sufficient answer. Anti-semitism has been around for a very long time. Hitler and the Nazis didn't invent it. Not by a longshot. It's been around through medieval times, and even during ancient Rome. There's alot of 'justifications', but they are all some variation of 'Jews are different, so it's easy to project my fears and insecurities on them.'
Hitler himself had many reasons why he hated Jews and it's something historians have studied for years. His father (whom he hated) was part Jewish. He was turned down for art school and blamed Jews.
But the most potent was that Hitler, like alot of Germans, blamed Jews (unjustly) for their loss in World War 1. The government of the Kaiser kept telling the German people they were winning the war. So when Germany surrendered, it was a major shock to them. And Hitler was a soldier in WW1. It was, by his own description, the best time of his life because he thrived on the comraderie with fellow soldiers.
To Hitler and those like him, the only explanation for how they went from being in a winning position to suddenly surrendering was sabotage. And Hitler blamed Communism and Jews. Which in his mind, were basically the same because he viewed Communism as a Jewish plot.
Hitler and other German anti-semites (and it's important to acknowledge not all were) blamed Jews for the struggles imposed by Versailles and everything else that went wrong.
Putting it as simply as possible:
All this was much more important than stories about what a Jew might or might not have done to Hitler in his childhood. There is no firm evidence that Hitler was anti-Jewish before about 1916. Beware of naive explanations.
For fuller answers click on the related questions below.
The Nazi's hated the Jews.
German soldiers lead by Hitler. The Nazis hated jews
The Nazis needed someone to blame for things which went wrong. For centuries Jews had been blamed, as there was no country to speak up for the Jews they were an easy target.
Hitler and the Nazis hated the Jews; there was no jealousy involved.
because they hated jews
Hitler and the Nazis hated the Jews; there was no jealousy involved.
because Hitler hated Jews and was bullied by the Jew!
Yes. The Nazis hated the Jews for what they were, not for anything that they did or did not do.
Because Hitler hated them
With cruelity. Nazis hated Jews enough to gas and burn them.
They hated Jews, and the communists
Hell no, many people hated Jews for thousands of years, mainly Christians hated Jews due to different religious believes.