In 1933, Hitler was made the Chancellor of Germany, and with the Nazi Party's use of propaganda, he was able to take advantage of his country's depression by promising to fix everything.
Hitler and Nazi party were easily able to win votes because Hitler promised civil peace, better economic policies, and a newfound national pride.
Nazi propaganda blamed the Jews for their nation's economic woes, so they openly encouraged anti-semitism - hatred of Jews.
Hitler was obsessed with nationalism and the Aryan race. Because of this, he planned to take over the world to make room for his "superior" Germans.
Hitler started his Final Solution by making laws that restricted Jews. Then he put them in abusive concentration camps before murdering millions.
Check out this animated overview of life in Nazi Germany.