The basic dynamic of the Ironborn arc in AFFC is that of a culture war in the wake of Balon’s death, working its way fitfully toward a long-overdue self-examination as a people…before a psychotic tripping sorcerer shows up, takes over, and enlists everyone in his quest to end the world.
Of course, he himself caused the vacuum by killing Balon, and even Asha’s plan had huge blind spots, so what the Crow’s Eye is in part doing is demonstrating how easy it is to hack into the Ironborn, like he’s revealing holes in corporate security by exploiting them. All it takes is an eyepatch and the promise of Valhalla, painted (unlike Gylbert Farwynd’s similar promise) in the right shade of red, and the crowd will happily pretend the smiling eye is all that matters. And the audience for that revelation, the person he is demonstrating that to, is unquestionably Aeron, especially in the light of “The Forsaken.” If the Dornish arc in AFFC boils down in the end to the dynamic between Doran and Arianne, the black oily stone at the heart of the Ironborn arc is the dynamic between Euron and Aeron. From the very beginning in “The Prophet”, the former is framed as a severe existential crisis for the latter, as the news of Balon’s death arrives:
Aeron Greyjoy had built his life upon two mighty pillars. Those four small words had knocked one down. Only the Drowned God remains to me. May he make me as strong and tireless as the sea.
Euron cast down the king and is now casting down the gods, and he wants to make his little brother watch. It’s part of a lifelong campaign dedicated not only to inflicting misery but also snuffing out identity and hope, in a manner similar to what Ramsay did to Theon; it’s Reek-ifying by way of the House of the Undying. This takes on both a personal and political resonance: as Euron deconstructs the “pillars” of Aeron’s life, he’s also doing the same to the revanchist Old Way self-conception gripping so much of the Ironborn, because Aeron has rebuilt himself post-abuse around precisely that mythos. Of course, this all has metaphysical implications as well, but those too are always tied to character and culture. Aeron remade himself as Damphair, the voice of god, and so Euron visualizes his apocalyptic ends as the death of gods, which simultaneously shows off his contempt for the Ironborn by executing their “laughable” humanized version of the Drowned God and presenting himself as the real thing, tentacles and all.
Which is why Aeron was made the protagonist of the AFFC Ironborn arc, and why he continues as our POV in the area even as GRRM flung Asha and Victarion far and wide in ADWD. Aeron’s reaction to Euron’s return drives that storyline, both the big picture and the more intimate stakes, and that’s expanded upon in “The Forsaken.” The end of the world is also a deeply personal nightmare designed to break him. Euron’s rise to power is woven out of these multiple story strands building on each other: the skin-crawling magical apocalypse, the expert hijacking of the culture war, and one man’s religiously-inflected gauntlet of torment underneath it all. All of which is a long way of saying that the plot was never lost here; the imagery of “The Forsaken” plunged us fully into the nightmare, but the ideas behind it had already been set up in AFFC, rooted in character dynamics.