Which makes me wonder why Bethesda even bothered having that prophecy attached to the amulet, did they even bother to look at TES history and realize it doesn't make much sense.
Yea. I cried my self to sleep there.
Anyway, I get the impression that they were trying to do this thing were you realize that what you've been told isn't the truth.
First with the talk about the Amulet of Kings. It's not just wrong on the account of who can wear it but it's also an Ayleid artefact. The Remanada hints at this by calling it Chim-el-Adabal. Second with Mankar Camorans talk about how the Aedra lied about the creation of the World.
Where it went wrong I think is in the delivery method of the first. People take loading screens as a fact, not as subjective information from an age old religion. Especially when it's the sole reason to actually find Martin. Combine it with a general lack of depth and it becomes the unquestionable truth because there is no obvious room for doubt. So it looks like a mistake rather then an intentional thing.
Mankars speech turned out to be a draft, not fact checked or anything, which obviously ruined his convincing power. Again this is probably compounded by the player never having heard much about the Aedra. It's kinda hard to believe you're being lied to if nobody ever told you about what.
In other words, great idea, poor execution. I'd blame the isolated way everything is set up because I wouldn't be surprised if that also reflects how the work is divided. Of course when you've got voiced dialogue and an large scale production, delegation becomes a necessity but it shouldn't end up showing such disconnects.