Predators are smarter than prey. Hare-brained is an insult; sharp as a fox is a compliment.
I have an evolutionary theory to explain this (full disclosure: except for reading voraciously on the subject, I am totally unqualified to have evolutionary theories).
A leopard chasing an impala can make a mistake, lose the quarry, learn from the mistake, and hunt more wisely on another day. If the impala makes a mistake, it becomes the leopard’s lunch.
Predators fail often;
Prey fail only once.
So it would be a waste of energy for prey to have a large analytical brain or to divert any resources into learning while running away. Better just to have long legs, good ears, and a healthy paranoia.
Thinking could be fatal.
It also doesn’t take a lot of smarts to eat grass.
On the other hand:
Predators learn terrain;
they can learn the habits of prey they’ve never seen before.
They learn where to wait patiently and when to pounce.
The play of kittens and cubs is as important to the development of their brains as it is to their muscles and their reflexes. And the play is full of stumbles and pratfalls – learning experiences, in other words.
I’ll bet tyrannosaurus rex was a genius compared to brontosaurus.