As a prior post indicated, the underlying reason Hitler rose and remained in power in Germany was because he was an anti-communist, and the perception was that he would maintain Germany against its enemies, the most dangerous of which by the 1930's was the Soviet Union.
It's forgivable for us to be a bit Western European Ethnocentric, as that is our culture, but the primary conflict of the Second World War was between the ideologies of Communism in Russia and Nazism in Germany. Interesting how both sides cultivated the cult of personality in Stalin and Hitler.
Hitler proclaimed a message that many people wanted to hear: the regeneration of a powerful Germany and a promise of economic prosperity. His policies against the Jewish peoples of Germany were also embraced by many non-Jews who stood to gain from these changes in the status of the Jewish people. As offensive as the anti-Semitic message was and is, it had an audience that wanted to hear it.
I think the greatest contributing factor leading to Hitler's rise to power was the aftermath of the Treaty of Versailles and the upheaval existing in the Germany's political and economic sectors during the Twenty's and Thirty's. Hitler was basically in the right place at the right time. Or, looking back now . . . in the wrong place at the wrong time! Germany's citizens were looking for reform and relief from the chaotic world they had been plunged into, and Hitler offered them the things they so desired. He was exceptionally gifted at public speaking and persuaded the masses that he was the answer to their problems. They supported him, raised him up to a leadership position, and things temporarily did change for the better. But, ultimately, he brought their country into greater ruin than it was in originally.
I think the first response sums up the factors that Hitler exploited to rise to power nicely. The only thing I will add is the unwillingness of other European powers and the United States to act in a firm way to resist Hitler, or to enforce the requirements of the Treaty of Versailles. (Of course the United States wasn't party to this, but it had made other disarmament agreements that it didn't stand by.) Hitler made it clear from the beginning that he was repudiating the terms of the treaty, and other nations failed to stand firmly enough against him. Two factors, I think, contributed to this: the domestic concerns of western nations resulting from the Great Depression; and the fact that many nations viewed Hitler as a strategic counterweight to Stalin.
I would say that it was the chaos that existed in Germany because of WWI and the Great Depression. Hitler came to power because the German economy had been so badly affected by the Depression and the reparations. He also came to power because people were so angry about the terms of the Treaty of Versailles.