Corruption arises in weak and inefficient legal and moral system
Humans are fallible beings, susceptible to various temptations. Public servants are also humans, therefore they often "feel the urge" to do something for themselves, or their friends and family, at the expense of public good. If their own conscience does not stop them, two things could - fear of legal punishment and fear of moral condemnation.
For the first thing to work you would need strict and clear control procedures, with assigned duties. Such systems do stifle corruption (at least on low and mid-tier of hierarchy) but they as a rule become bureaucratic and inflexible. Second thing, morality of certain society, is elusive category. It depends on culture, tradition, religion etc ... It is usually eroded when legal system does not work (" hey, if I don't steal that somebody else would" ) .
Future dictators usually promise to repair both public morality and laws, but morality is more important do them. Hitler rose to power during the time when Weimar Republic did fall in the depths of decadence. For example prostitution and crime boomed in Berlin, and while technically still illegal, they were silently accepted. Hitler seized opportunity to blame Jews, communists and parties then in power for this moral catastrophe. He didn't blame insufficient laws and didn't promise legal reform - because he didn't need them. Instead, he simple said that groups responsible for this would be punished (laws notwithstanding), and promised to restore traditional German morality.
Hitler did not hide that he is not interested in democracy, and that he required obedience from German people, asking for dictatorial powers. Question is why did they accept this ? One of the reasons is that large part of Germans deemed current (Weimar) system as insufficient and useless. Hitler's promise of strength, not restrained by laws appealed to them, because they already lost faith in a possibility that something could be done in that existing system.