I think Bezos referred to the mindset of the people who live and die by the success of the company - namely the founders and executives who are responsible for making sure it succeeds.
Do they live and die by the success of the company. If the business starts to decline who is terminated first. The founders and executives. The audience for the letter from this quote is taken is not only founders and executives, it is Amazon employees, investors, potential investors and analysts, i.e., the public.