I don’t think that the example of kings losing their powers really supports your thesis here. That wasn’t a seamless, subtle process of power slipping away. There was a lot of bloodshed and threat of bloodshed involved.
King Charles I tried to exercise his powers as a real king and go against the Parliament, but the people rebelled and he lost his head. After that, his son managed to restore the monarchy, though he needed to agree to some more restrictions on his powers. After that, James II tried to go against the Parliament again, and got overthrown and replaced by another guy who agreed to relinquish the majority of royal powers. After that, the king still had some limited say, but he they tried to do unpopular taxes in America, the colonies rebelled, and gained independence through a violent revolution. Then next door from England, Louis XVI tried to go against the will of his Assembly, and lost his head. After these, the British Parliament started to politely ask their kings to relinquish the remainder of their powers, and they wisely agreed, so their family could keep their nominal rulership, their nice castle, and most importantly, their head.
I think the analogous situation would be AIs violently over-taking some countries, and after that, the other countries bloodlessly surrendering to their AIs. I think this is much closer to the traditional picture of AI takeover than to the picture you are painting in Gradual Disempowerment.
On the other hand, there is another interesting factor in kings losing power that might be more related to what you are talking about (though I don’t think this factor is as important as the threat of revolutions discussed in the previous comment).
My understanding is that part of the story for why kings lost their power is that the majority of people were commoners, so the best writers, artists and philosophers were commoners (or at least not the highest aristocrats), and the kings and the aristocrats read their work, and these writer often argued for more power to the people. The kings and aristocrats sometimes got sincerely convinced, and agreed to relinquish some powers even when it was not absolutely necessary for preempting revolutions.
I think this is somewhat analogous to the story of cultural AI dominance in Gradual Disempowerment: all the most engaging content creators are AIs, humans consume their content, the AIs argue for giving power to AIs, and the humans get convinced.
I agree this is a real danger, but I think there might be an important difference between the case of kings and the AI future.
The court of Louis XVI read Voltaire, but I think if there was someone equally witty to Voltaire who also flattered the aristocracy, they would have plausibly liked him more. But the pool of witty people was limited, and Voltaire was far wittier than any of the few pro-aristocrat humorists, so the royal court put up with Voltaire’s hostile opinions.
On the other hand, in a post-AGI future, I think it’s plausible that with a small fraction of the resources you can get close to saturating human engagement. Suppose pro-human groups fund 1% of the AIs generating content, and pro-AI groups fund 99%. (For the sake of argument, let’s grant the dubious assumption that the majority of economy is controlled by AIs.) I think it’s still plausible that the two groups can generate approximately equally engaging content, and if humans find pro-human content more appealing, then that just wins out.
Also, I’m kind of an idealist, and I think part of the reason that Voltaire was successful is that he was just right about a lot of things, parliamentary government really leads to better outcomes than absolute monarchy from the perspective of a more-or-less shared human morality. So I have some hope (though definitely not certainty) that AI content creators competing in a free marketplace of ideas will only convince humanity to voluntarily relinquish power if relinquishing power is actually the right choice.