Also this is my speculation, but I think Nightreign might be developed only as part of the deal to purchase back the IP, since it's still being published by Bandai Namco.
Nightreign was in conceptual phase before
https://www.pcgamer.com/elden-rings...-tarkov-for-a-little-multiplayer-inspiration/
In particular
The director told IGN that the game's popularity won't "affect what we are going to create next," and that FromSoft will "keep creating the game that we want to create, and that's our policy"
Fromsoftware don't make games they are absolutely willing to do. It doesn't matter what people want. They have always stepped outside their comfort zone. Making a multiplayer title forces Fromsoftware to improve on some aspects where they struggle. The AI for example has different target priorities in Nightreign to better handle group fighting and is not based purely on closest target vs last aggro.
Furthermore, Elden Ring Nightreign IS an Elden Ring game
In the CNT you can actually see the Shadow form of those who died and went before the Erdtree and the Scadutree, like the proto giants who spawned from the primordial life brought by the first meteor, and laid the foundation of the Lands Between themselves. They are now wandering aimlessly with a body of tree roots.
Limveld is connected to the Lands Between, the Spiraltrees appear as shades, with the Two Fingers growing from the Divine Tower the Ancient Dynasties created to support them as braces.
Miyazaki, like Armored Core 6, was involved in the conceptual phase of the game and the world is likely very coherent to Elden Ring.
If Fromsoftware wanted to recycle assets aggressively, he would reskin them in a bigger fully priced NOT! Elden Ring project that can reuse a lot of assets, instead of straight up embracing heavy lore elements
There's nothing in Elden Ring that Myazaki couldn't come up on his on
Reportedly, what GRRM did was create a very early backstory for the world and some of the characters, then FS took that and greatly altered and twisted it. Most of the iconic elements of the game literally are done by Miyazaki himself. So I think you're totally right. I think it was largely a marketing push from the publisher, or maybe a personal desire of Miyazaki to collab with Martin.
Neither Miyazaki nor Bandai (who had zero creative direction on Elden Ring) need to use GRRM name for marketing. If Miyazaki wanted his stories to get awards, he wouldn't be famous for obscure stories that require investigation and exploration over more common and popular forms of storytelling.
He doesn't care that most people wouldn't notice a small building of Eternal City architecture in the outskirts of Leyndell with heretical Tree iconography indicating the cult of the Sacred Trees started as underground religious movement during the Ancient Dynasties much like Christianity during Rome, or that the Grand Cloister in the Lake of Rot is styled after the Temple of Isis, Goddess of Death who saved her kidnapped brother and sent him to the Realm of the Dead.
No Miyazaki game is going to win any awards for writing or be a selling point, its just his style.
