The promise of prosperity, mostly. Under the NSDAP economic program, industrial workers would get full employment and much better conditions, the rural poor would be resettled on their own land in the conquered East, artists and other intelligentsia would enjoy state patronage, industrialists would get preferential access to resources and markets in German satellite states and so on and on. A generic "middle class" German would have been especially susceptible to the rising-tide-lifts-all-boats sentiment and benefited particularly from the exclusion of Jews and other minorities from the professions, as well as participating in a variety of programs and subsidies technically aimed at the working class, such as subsidized radio sets, holidays and so on.

Source:

Gotz Aly, Hitler's Beneficiaries