What could you be intelligent at if you could just copy yourself a myriad number of times? What could you be good at if you were a world spanning set of sensors instead of a single body of them?
Body doesn't need to mean something like a human body nor one that exists in a single place.
"Hmm, oral traditions are a pain in the ass lets write stuff down"
"Hmm, if I specialize in doing particular things and not having to worry about hunting my own food I get much better at it"
"Hmm, if I modify my own genes to increase intelligence..."
Also note that intelligence applies resource constraints against itself. Humans are a huge risk to other humans, hence the lack of intelligence over a smarter human can constrain ones resources.
Lastly, AI is in competition with itself. The best 'most intelligent' AI will get the most resources.
For example, if you focus on oral traditions you experiment and create more poems, songs, etc. If you focus on preserving food you discover jams, dried meat, etc.
Is it useful to focus on everything, or global optimal? Is it possible?
Also regarding competition and evolution, what stopped humans to get more capable brains? Is it just resource constraints, like not having enough calories(not having mini nuclear reactor with us)? Or are there other, more interesting causes?
They'll definitely be aligned on partial ordering. There's no "smartest" person, but there are a lot of people who are consistently worse at most things. But "smartest" is really not a concept that I see bandied about.