Can we count mammals and corvids separately if their common ancestor was already set on the path to intelligence? The amazing book Other Minds by Peter Godfrey Smith hinges it's argument on minds evolving twice, on the fact that the common ancestor of humans and octopi was probably a simple worm-like creature that had little or nothing in the way of a brain or consciousness.

I have to imagine that corvids and mammals had a common ancestor with more working brain structure. Though maybe you can make the case that "intelligence" showing up later on isn't the same thing as simply having a brain.

But it's much more impressive to me that there's convergent evolution from brainless to brain-having, than from brains to intelligent brains. Don't get me wrong, it's still awesome but doesn't feel like an out of nowhere path for natural selection to take.

A very important fact to remember is that brains are not a requirement for intelligence (in the very broadest sense, not the more specific one used here), nor even neurons. All cells have some amount of computational power and can meaningfully react to their environment; a common example is white blood cells quickly adapting to pathogens to try to destroy them. Networks of cells are even more powerful, such as slime mould exploring the space around it until it detects nutrients and then channeling all resources in the direction of such nutrients. Plant roots have sophisticated sensory abilities detecting numerous kinds of chemicals in the soil, and actively search for nutrients and avoid contaminants. Even jellyfish, some of the simplest animals, long thought to be essentially passive, in fact detect and actively steer themselves towards prey.

Intelligence actually exists at all levels of life, and brains are just an apex of achievement, just like eyes are an apex achievement of light-sensing mechanisms that similarly exist all around the tree of life.

Agree. Birds still have two eyes, two arms, two legs, heart, liver, kidneys, etc. there's clearly a common ancestor after the basic vertebrate anatomy evolved.