The Event happened, you've finished the prologue, you're in an open world.
In Baldur's Gate you could go straight to Nashkel, or go to the Friendly Arms Inn (or explore the world as you saw fit). Nashkel and the Friendly Arms would still have been there for you.
What if you had a 3rd path you could've taken, which would be "Your" path (the Characters path, the story/main-story) and you can explore Nashkel, help out with the mines, if you wanted to. What if the entire story with Sarevok could've been a side-quest and you, the character, has a bigger purpose than that.
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