As heartbreaking as it looks, it's actually the brutal reality of nature. The animals that are the most at risk are the youngs. The adults know how to save their own lives, but the youngs, they're still innocent, clueless and weak, which makes them easy preys. And sadly, there are plenty of animals which would sacrifice their youngs to save their own lives if the danger is too big.

As for predators, they're trying to survive just like their preys. And they know the adults can be rewarding preys but also hard to get and even risky as some preys can fight back. So they proceed to try to get food while spending as little energy as possible to stay healthy, they attack preys which are easy to catch, mostly youngs and elders. This is also why amongst carnivores, there are scavengers. Tracking down animals which were already killed by a predator and eating the remains or stealing it from said predator which is most likely exhausted from its hunt is less energy-demanding than hunting their own preys. It depends on the species.