Of course, Castro didn't want to take too many risks and therefore he sacrificed Mane to be replaced rather than having to cause problems with Cristiano. I hope that in the next match Cristiano will sometimes realize that the team's victory is above all else.
It should be that all players are wise. Logically, Mane is 31 years younger. He has better stamina than Ronaldo. It should be possible to replace Ronaldo is the right decision. Castro could replace Ronaldo with a defensive midfielder or defender and push Mane forward. This can be done to take advantage of the counterattack. In addition, they strengthened the defense. Losing 2 points is quite meaningful. With the condition that the difference in points is not much. Indeed, managing Star Players will be more difficult and it becomes Castro's burden.
Sometimes even great players with a lot of experience like Ronaldo will also have difficulty when he has no other way to break into the goal but the positive side is that sometimes it makes his opponent's defense focus only on him. However, I still think that every now and then Castro has to have the courage to replace him with a younger and fitter player so he can press hard into the defensive area and create opportunities for his teammates on the field.
Talking about stamina, Ronaldo is actually still above Mane and we can see that even though occasionally Ronaldo just walks casually, he doesn't look like he's tired and when he gets a chance he will run as fast as possible to meet a pass from his partner. Meanwhile, Mane may be younger and because of that, Mane should be able to use his stamina to press or make breakthroughs with his dribble, but unfortunately that is no longer there. After Mane last suffered an injury when he was still at Bayern Munich and as we can see, maybe now he only has half of his prime remaining.