What really irks me about this particular issue, I don't know if it's just an oversight on Larian's part, or if we're supposed to infer things about the world and Shar from this.
We can infer that Larian wanted this reveal (association?) to be a mystery and so they rewrote/ignored a significant part of Forgotten Realms history in order to...uh..."make it work"? It's kind of like expecting the average resident of Europe plus a good chunk of western Russia (I'd say "Earth", but Faerun is much smaller than the surface area of this planet) to not at least get the gist of Satan/The Devil/Beelzebub when they're asked about that mythological/religious figure. The difference here is worse, though, because priests of the Realms truly can raise the (un)dead, conjure demons, curse/sicken/slay with but a touch, et cetera. Finally, gods manifest themselves in ways across the spectrum from subtle to overt: from ephemeral baleful eyes in the darkness to full-fledged avatars walking the soil.
