You need to actually do some NGO / oversight / ethics work that matters for a while, then you're the perfect candidate for these kinds of roles where you'll be able to do a lot but ultimately not be able to change anyone's already made up opinions within the company. These big companies have other roles than just head of ethics, even sometimes Civil Rights officers, etc. They make a lot but don't get to do anything and a lot of times they just use these jobs to make some money then jump back to non-profits, etc.