Evolution isn't aimed. A T-Rex needs to be good enough to hunt enough food.

Our ancient ancestors smashed the skulls of animals killed by African predators to eat the brains, smashed bones to eat the marrow.

Later as our ancestors became bigger and stronger they hunted and needed to communicate with each other to effectively track and take down an animal. Maybe they needed twenty words. Chickens have three words (or cluck patterns)

At the same time women collected stuff and needed to share how to identify this from that with younger women. They might have needed a hundred words.

Then those who could talk better were more attractive to the other sex than those who couldn't (even now being well spoken is attractive) then a few millions of years later we're making stone knives, hammers, axes; then ten minutes later aeroplanes and machine guns

In short: we had it hard enough we needed to share information. We later found communication sexy. T-Rex had no such trouble. We seem to be the only animal that solved "scavenging is dangerous" and "hunting is hard" with talking to each other rather than by getting bigger and getting claws or vicious teeth

I understand we selected for tall by fighting humans

The difference is that they decided not to be parasitic narcissistic global suicide "apex" who gave no fucks, literally, about our will-no-longer-exist "children."

You're so narcissistic you will refuse to admit that they weren't stupid. The very way you will chose to be exactly that by denying the obvious as I lay it out so blatantly that your ego cries and denies ad infinitum.

Edit: Yeah and it's okay. Those downvotes will save anyone's life on this planet. Adiós!

Now you get it. :)

Corvids and psittacines display human child level intelligence. They use tools. They recognize other people. Hell the psittacines can mimic speech.

I personally suspect it's a matter of energy density. Birds have to use almost all of their available calories on flying. Doesn't leave a lot of energy left over for a massively hungry brain. No clue what's holding back penguins, emus, and cassowaries.