You are correct. There are a lot of people misinterpreting where abstract thinking and problem solving takes place in the cognitive chain.

You're also not a purely "rational actor" who makes choices devoid of underlying impulses, of course. There's an interplay between the two.

Your brain makes decisions bureaucratically.

>But then... how does anyone ever go on a diet? I think that is a massive hole in this theory. We don't always follow our body's instructions.

Your subconscious takes what you know about the dangers of obesity, or your lack of dating success, or the amount of stress that your mother calling you fat causes you, and decides that eating less would actually be better for whichever of those reasons. Then it tells says, "We're eating less for a while", and again, your conscious mind tries to guess why it got this order and come up with an explanation of why... I didn't say that we always follow our bodies' instructions. It was just one purposefully simple example.

Think of the subconscious as upper management and the conscious mind as the worker on the shop floor. Except the worker, for their own sanity, has to believe that management is competent. So directions come down from on high, and even though the worker has no understanding of what went into the deliberation process, they piece together the best explanation they can from what they have available.

Basically, it's exactly what you do any other time you have incomplete information. What do you genuinely know about what Pitun thought before he invaded Ukraine? Basically nothing. But if you have any interest in the story, you probably immediately had some strong guesses at what you thought he must be thinking. Well, it's exactly like that except you think you're making the decision, so you don't think your guesses about the real motivations are guesses.

>You and some others are contradictory here. Who rationalizes what?

>If brain is just a matter interacting and produces output based on computations inside itself, who rationalizes that afterwards?

>There is no one out there. It is still the same dead matter interacting and nothing else. Lifeless atoms do not need to explain anything.

There is nothing contradictory here at all. If you want to insist that the conscious self is also an illusion, then that only makes it necessary that conscious choice be an illusion.

Our brains developed extra capacities that allowed us to be able to store new and complex, even second hand, experiential information to supplement our inborn instincts for processing during the subconscious decision process. Consciousness seems to be an emergent property of this additional storage and computational hardware. Apparently it tends to increase survivability, otherwise the pre-conscious step in human evolution would have won out.