Luck is a HUGE element in this story. In no particular order, some of the luckiest ones are:
-Durge happening to be on the same Nautiloid that Thrall Emperor uses to steal the Astral Prism - remember that the Brain had nothing to do with placing Durge there, this was done by an uninfluenced Orin (remember: Durge becoming a pawn in the Design simply meant that the Brain simply looked upon it's disgraced master with disgust and would have used him as a lowly soldier or worker - at the very least there is nothing to suggest that the Brain somehow influenced Orin to place Durge in that Nautiloid)
-That dormant Mind Flayer colony just so happened to also house a dormant Elder Brain and at least one Nautiloid
-Emperor failing to appear as Balduran (aka himself) in Dream Visitor segments is incredibly unlucky