The skull of a Bengal tiger rests along side the skull of a domestic cat.
Notice the proportionally smaller braincase and eyes in the tiger, and the much larger flanges for muscle attachment, in comparison to the overall size of the skull.
As animals scale up in size, more muscle is needed to bear the additional weight and counteract the effects of gravity. To anchor the increased mass of the muscle, bones become more robust. Thicker, heavier, with larger flanges, and deeper hollows to provide the additional muscle with leverage.
It’s a cyclic system. More muscle is needed to support heavier bone which in turn supports more muscle…etc.
You’d think it could go on forever, but as animals become larger and more powerful, they also become heavier. For land predators, the cycle reaches a cutoff size when the increasing weight begins to negatively affect agility, maneuverability, and the ability to successfully catch prey.