With the same reasoning management could say that ethics is the responsibility of investors who decide about how ethical a company should be and customers who may pay for the non-ethical product.
58.5% would not write code for an unethical purpose, and only 4.8% would unconditionally say yes. 79.6% think that they have to consider the ethical implications of code they write.
The 57.5% who said that management is most responsible for ethical decisions would probably agree that developers are responsible as well, just maybe not as much as management (who have far more agency to just assign the task to someone more willing if anyone refuses). Since the options were limited to be mutually exclusive, those considerations were not captured by the survey.