Why is the skull formed by the strongest bones?

The skull must protect the animal’s brain from various injuries; inside the skull there is an organ, without which the animal could not live even a minute. In order to protect an important organ, bones have thickened and hardened during evolution. Also, if the skull is injured, but the animal does not die at the same time, the cracks formed in the bones will heal to form an even stronger bone. Thus, the body protects itself from external negative consequences.