No doubt Cristiano Ronaldo will be a great coach if he decides to be a coach after he calls it a day in his football career, but Cristiano Ronaldo made it clear that he will not be a coach after he retires from football. Cristiano Ronaldo is a businessman, so I am not surprised with the 15 percent of Al Nassr ownership.
he's just realistic that there's no guarantee that if he chooses to become a coach that it will make him a great coach. the choice to become a businessman and brand ambassador might seem more beneficial to him, because he already has popularity and achievements as a footballer, so he doesn't need to become a coach and start a new career on that... and by becoming a businessman and brand ambassador it can make him focus more on his family and the things he loves and the projects/businesses he wants to develop. so there will be a lot of advantages he gets compared to just being a coach and risking more things to become a qualified coach for his team.