There were a lot of different things that happened that caused them to attempt to eradicate Jewish people.
One reason is their idolized Perfect society.
The perfect society was basically what they felt was the perfect look for humans. Meaning white skin, blonde hair, and blue eyes. They murdered thousands of, not only Jews, but those who were crippled, who were Black, and others with different illnesses. They felt that not only did you have to look a certain way, but you had to act a certain way so they also murdered those who were gay. As you know, the Jewish community did not fit into their "Perfect Society".
Another reason was that they were in a deep financial crisis due to WW1.
After the first World War, Germany had to pay for many damages. This left them in a depression. To exit this crisis, they needed help. A man named Adolf Hitler grew the Nazi party and started explaining that they would get through this depression if it weren't for the Jews. He explained that they had more money and it was their fault that nobody else had any. Eventually the people started looking up to Hitler as a leader. They followed his orders thinking he would help them get out of the depression.
Hope this helped! :)