In a different thread, we're discussing 'how things originally were intended' and I suspect this has a lot to do with all this.
Any good adventure story introduces what it's about in the opening sequence. That's why Game of Thrones starts with the White Walkers, Star Wars with Darth Vader chasing Leia, Fellowship with Sauron and the Ring and so forth. I believe that years ago, when they made the opening cinematic as a trailer - the plans for the plot were a lot different. I think, that originally, the Emperor was literally the leader of the remaining Illithid Empire, which is about to get utterly wiped out by the Gith. Indeed, as pointed out somewhere here, the emperor's armor is a fair bit distinct from the other Illithid you encounter, but is exactly that one from the trailer/cinematic. With that, you were intended as the Emperor's Chosen One, but, well, you know. You're also otherwise engaged to Vlaakith, Mystra, Shar, Mizora or otherwise Vampowered.
As the narrative was changed and Daisy the seductive Illithid Dream character was integrated with the Emperor, who also suddenly turned into someone else for just one line of unnecesary dialogue, the Nautiloid made a whole lot less sense - but not so much that they'd scrap it and redo all the expensive cinematics.
it's a... Well. It's a bit of a 'let's not think about it too much' kind of thing, now.
Idk, Dead Three iconography was featured pretty early in EA. The Emperor's plot being more Illithid-focused makes sense, but I think the main idea of the game was always going to be centered on Baldur's Gate and Bhaal in some way.
