> most of the creatures that thrive don't have what we consider intelligence, so it's not that evolutionarily important

I dispute that this is because they don't poses intelligence. Whenever we find an animal displaying some ability we had said required intelligence — language, tool use, self-awareness, solving abstract puzzles, driving a car — we seem to change our definition of intelligence. Just like we have done with A.I., although probably because we want to eat the former and make slave labour of the latter. ;)

(Am vegetarian, please don't eat me, oh robot overlords!)