What is an example of how an effort to please one group of stakeholders eventually pleases all stakeholders?

One excellent example of this is the efforts to reduce carbon footprints. Originally, these were corporate social responsibility initiatives undertaken for ethical reasons. These actions benefited all stakeholders, including employees, shareholders, customers, and suppliers by helping to ameliorate global climate change.

Reducing energy consumption, though, had major other benefits. Energy costs money. Reducing energy use by such tactics as passive solar design, installing solar panels in parking lots, changing to energy-efficient light bulbs,  turning off lights automatically when they are not in use, and other energy-saving steps cuts costs. Reducing a firm's energy costs means either greater profits or the ability to pass cost savings on to customers. 

One specific example of this is installing solar carports in warm sunny climates such as the southern and southwestern United States and southern Europe. Placing solar panels in parking lots not only generates energy but shades cars from the sun. This means that customers, employees, and other visitors get the benefit of shade for their cars and the company gets the energy generated by the panels.