The short answer to this is that the Nazis’ economic policies caused the German economy to become healthier, at least in the short term. Because Germany had been experiencing such severe problems economically, people came to approve of the Nazis much more than they would have if the economy had not improved.
When Hitler and the Nazis came to power, the German economy was in a bad state. The Great Depression was in full swing and Germany was suffering. Hitler attacked the economic problems vigorously. He implemented major programs of public works. This was beneficial to the economy because it increased government spending dramatically. This meant that more money was being pumped into the economy and more jobs were being created. Many of the jobs that Hitler created had to do with rearming Germany. Hitler also did things like crushing labor unions and making strikes illegal. However, people did not mind this as much as they might have because the economy seemed to be getting better.
In bad economic times, people will tend to be happy with any government that improves the economy. Since Nazi policies improved the economy, they made people like the Nazis and thereby helped to keep them in power.