There are many contributing factors and possible theories as to why Hitler and Nazi Germany did not like the Jews:
"One reason the Jews were killed by the Nazis was that the Nazis were jealous that the Jews..the Jews had the riches and the main businesses, and a great life.
Another reason was jealousy. Some Jews were successful and held powerful positions in Austria and Germany in the 1920s and 1930s. At the same time, the world was suffering in the Great Depression. For various reasons, including war reparations for World War I, Germany was being hit the hardest by the worldwide economic depression. Successful Jews were envied and blamed for "taking German jobs."
During World War I, Communism was on the rise. Lenin's Revolution had forced Russia out of the war. The German Army at times faced near rebellion among their own troops. This contributed to Germany being forced to sue for peace. Since some socialist/communist leaders were Jewish this was exploited as another reason for Germans to hate Jews. Hitler often spoke of Bolshevik (communist) Jewry. There is still a strong association in some people's minds between Jews and leftism of various kinds.
Another reason for Hitler and Nazi Germany's hatred of Jews was that Hitler and other Germans absorbed some of their parents' racism. Anti-Semitism has a long history.
In addition. some Germans held to the belief that "Jewish bankers" were responsible for the Treaty of Versailles because they stopped funding WWI.
Another factor was The Balfour Declaration of 1917 which supposedly proves that Jews betrayed Germany in World War I. According to one who holds this theory, "During the Great War (World War I), members of the Zionist Jewish elite bartered with England and promised to bring the United States into the war in exchange for Palestine. This is the root cause of the belief that the Jews contributed to the defeat and subsequent economic r**e of Germany in the post-war years." However, this wasn't something mentioned much in Germany and seems to be a post-1945 preoccupation of a few anti-Zionists.
Jews became a scapegoat for all of Germany's economic problems. (According to this racist sentiment, "international Jewish financiers like the Rothschilds, Oppenheimers, Bilderbergs, etc., plunged the world into a war for their business profit.")
Another factor in this issue was that Hitler and many Nazis were influenced by an anti-Semitic book called "Protocols of the Learned Elders of Zion." The Protocols of the Elders of Zion (Russian: "Протоколы сионских мудрецов" or "Сионские протоколы") is a fraudulent text published in the Russian Empire in the early 20th century that purports to describe a plan to achieve world domination by Jews. Numerous independent investigations have repeatedly proven it to be a hoax by Okhranka, the tsarist secret police; most notably, a series of articles printed in The Times of London in 1921 revealed that much of the material in the Protocols was plagiarized from earlier political satire that did not have an antisemitic theme. Since the Protocols appeared, its earliest publishers have offered vague and often contradictory testimony detailing how they obtained their copy of the rumored original manuscript. Nevertheless, some people continue to view the Protocols as evidence of a conspiracy, especially in parts of the world where antisemitism is widespread. It is also frequently quoted and reprinted by antisemites, and is sometimes used as evidence of a Jewish conspiracy, especially in the Middle East.
Another aspect of this issue is that some claim that Hitler's mother was half-Jewish and he was ashamed of this. (Hitler's grandmother on his father's side was a housekeeper in the home of a Jewish family. When she left she was pregnant with his father.)
Another factor which may have lead to Hitler's hatred of Jews was a rumor which says that in Hitler's youth he slept with a Jewish prostitute and contracted syphillis.
There is one theory that says Hitler hated Jews so much because of his mother's death. She died in a hospital and the doctor may have been Jewish. There is a story that the Jewish doctor needed to examine Hitler's mother's b****t because she had b****t cancer. Hitler resented the man touching his mother intimately. Alternately, he hated the doctor for not being able to save her. One piece of evidence that contradicts this theory is a letter from Hitler to the Jewish doctor, where he apparently thanks the doctor numerous times for his help.
Another factor in Hitler's hated of Jews was that
Hitler lived in Vienna from 1907 to 1913 and those were the most difficult years of his life. Hitler was trying to become an Architect or to make himself a name in field of arts. He was twice rejected from the Vienna Academy of Fine Arts. The second rejection by the Academy was one of the most traumatic experience of his life; all his dreams were shattered. After discovering that four out of seven professors that rejected him were Jewish he blamed the Jews for his failure.
The Nazis had a vision of an Aryan German race that did not include Jews and many other groups of people.
Here is an example of Hitler's anti-Semetic racism from a speech given in Munich in July 1922: "His is no master people; he is an exploiter: the Jews are a people of robbers. He has never founded any civilisation, though he has destroyed civilisations by the hundred...everything he has stolen. Foreign people, foreign workmen build him his temples, it is foreigners who create and work for him, it is foreigners who shed their blood for him."
Another aspect of this issue is that Jewish communities tend have a very strong group collective mindset. They differentiated themselves from other Germans. This made them easier to single out for hatred.
Some say Hitler and the Nazis were simply opportunistic demagogues. Inciting hatred of the Jews was the means to an end. The Nazis used hatred of the Jews to unify the German people and create a new German empire. Nothing unites a people more than when they believe they are constantly under attack and fighting a common enemy. The Jews were convenient enemies. After propogating this idea of Jews being the scum of the earth so passionately, Hitler and the Nazis may have deluded themselves into believing it more deeply.
The Christian religions blamed the death of Christ on the Jews. One can see in the Bible the statement that the Jews demanded the death of Jesus, and said, "let it be upon our heads and that of our children." This became an excuse to abuse the Jews for more than a thousand years. It was not until the 1960's (I think) that the Catholic Church stated that the Jews were NOT to blame for the death of Jesus.
In the 1930s there was a lot of anti-Jewish feeling and resentment in the Western world. Many Jews who wanted to escape the persecution in Germany were refused entry into the US and other European countries.
As a nationalist party, any group that felt it had a higher loyalty than the nation was going to be in for trouble. This is why the Nazis tried to suppress all religion, and even set up its own secular Church. Jews tended to have family links outside Germany, especially in Russia or the US, which would make them much harder to indoctrinate with nationalist bull.
Anti-semitism has been rife throughout European history, largely because they were a distinct, easily identifiable group, who refused to integrate. (Those who really wanted to integrate converted.) Of course now we see pluralism as a virtue, and a variety of ethnicities and religions as a positive thing. However, if you want to set yourself up as the totalitarian dictator of a Nation then you have to establish a clear identity for that nation and stick to it; variety is an anathema.
Another key element of a dictatorship is fear, and a visible scapegoat experiencing the wrath of the state is a good way to keep people from stepping out of line.
The last factor I want to present is that of Hitler himself:Hitler was an unstable man. He was suffering from a manic-depressive psychosis ((http://brainmind.com/Hitler3.html),Hitler's
mental instability was also in evidence before he became a tramp, for he appears to have experienced psychotic episodes while living with August Kubizek. As noted, Hitler believed his thoughts could penetrate walls or that he could communicate with others by thought alone--which suggests he may have been delusional and hearing voices. Hitler in fact admitted to hearing voices when he was a soldier and after he became Chancellor of Germany.
More obvious evidence of psychosis, however, was Adolf Hitler's periodic loss of emotional control, coupled with periods of weeping, or conversely, extreme rage." ((http://brainmind.com/Hitler3.html)
All of these mentioned factors which experts have elicited in various scholarly texts contributed to Hitler's and Nazi Germany's hatred of Jews.