Why, moving to power, did the fascist parties strive to comply with the norms of parliamentary democracy?

I believe that it was fundamentally important for the fascists to come to power in a legal way. Thus, they demonstrated that they rely on the support of the general population and were able to create a new ideology of the German people. Hitler and his associates, indeed, enjoyed particular popularity among the inhabitants of Germany. After the defeat in the First World War, it was the National Socialist Party that proposed a new development plan for the country, which helped it regain its economic power and take its place in the political arena.