Why were the Nazis so successful?

Answer 1

The NSDAP was notoriously efficient, in that all of Germany had some participation in the policies of the Third Reich (not necessarily involving in the "Final Solution"). The Wehrmacht of Germany had also become a force that was known to be strong on the battlefield and helped aid Nazi Germany in taking over. With the often debated term "blitzkrieg", the German army swept through many countries and secured a strong foothold for the Third Reich to install its policies. And away from the battleground, the SS and Gestapo dealt with internal and external matters of arresting, deportation, extermination etc. This coupled with many other factors (such as the recovery of WWI for many other nations) made the Nazis very successful for the first years of WWII.

It should also be noted that the Nazi Party was successful because of the role of the citizens of Germany at the time. Without the mass support from Germany, the NSDAP would not have been given the small power they held before the Enabling Act and the continuing support once they achieved complete control.
The Nazi's were successful in Germany for several reasons. The German economy situation was bad before the group came into control over the government. The current situation in general was bleak, with many of the buildings in Germany destroyed. Also, the Nazi's put the blame for what has happened after WW1 on the Jewish people, providing a scapegoat for people of Germany to blame.

Answer 2

they gained from their failure to take power by force.

They gained publicity and popularity over the following fifteen years, so much so that they went from an extremist fringe party to the main party in the country and were asked to form a government.