Why did so many German doctors join the Nazi Party early?

During the Weimar Republic in the mid-twentieth century, more than half of all German physicians became early joiners of the Nazi Party, surpassing the party enrollments of all other professions. From early on, the German Medical Society played the most instrumental role in the Nazi medical program, beginning with the marginalization of Jewish physicians, proceeding to coerced "experimentation," "euthanization," and sterilization, and culminating in genocide via the medicalization of mass murder of Jews and others caricatured and demonized by Nazi ideology. Given the medical oath to "do no harm," many postwar ethical analyses have strained to make sense of these seemingly paradoxical atrocities.