Because he isn't. Withers catches Act 3 Bomb-Gale's soul before Mystra can whisk him away to Elysium and brings him elsewhere because Gale apparently still has stuff to do.
Boy I hope not. Withers might be an upgrade for Durge but it's a downgrade for Mystra's faithful. lf Gale converts from the worship of Mystra to Withers he's going to give up eternity in a library for a job writing down the names of people who have died. There's a reason why the god of data entry doesn't have many followers.
If Withers took him why didn't he bring him to the party? Come on bone man if you can find Tara you can find Gale.
On the meeting with Mystra
Interesting difference in dialogues I got. They were almost the same but - from memory - Mystra told Gale that the first thing the orb consumed were his talents. Now it's not clear what his talents were I took her to mean his chosen abilities. I took the following you progress meant following after orb stabilization but I concede that your interpretation of that is the better one.
Mystra probably knew that Gale screwed up and waited to see if he could complete the quest that fate handed to him.
With Gale as a companion I was able to give him advice on what approach to take with Mystra and my cleric chose something like 'ask for her forgiveness' I suspect that the there is some sort of counter for the origin as well that determines how that conversation goes.
There are similar counters in the game - while I never created an undead I did use Glut's spore servant power once and afterwords my Tav had lots of edgelord things to say when selected . . . Took a while for her to reset to "these boots have seen everything"
"Go, Gale of Waterdeep. Your life is your own at last. It's time you went and lived it."
That does seem like a good ending for Gale. It seems like a story of maturity.
On the worth of a single mortal lifeLarian's approach to this is strange. On one hand soullessness is the looming danger of illithid transformation and on other hand mortal life is treated as more precious than eternal life. Soul coins - which in the lore experience terrible agony when burned in an infernal machine - are simply potions that make Karlach really hot. Karlach's transformation into a soulless monster than hungers for human brains is treated as a transformation into an existential philosopher. Larian's attitude on souls is . . . weird. It seems more like DOS2 - where souls are simply sources of "source" - than Faerun.
On the false endingOne of the many, many problems with the endgame is that it doesn't explain why the gale-bomb fails to kill all the tadpoles at moonrise but does in the endgame. I think they anticipated that a Cleric of Mystra would object to this depiction of Mystra - which is why they gave my cleric the "this doesn't sound like her" / "she should trust in my abilities" lines
I don't know if I would be happy with a more rational, we should free ourselves from the gods playthrough myself because many of Gale's lines there sound like he's blaming his ex for a decision he made. Which, I think, is one of the motivations behind people finding reasons to see Mystra as some sort of monster than grooms children.
Having seen the origin Gale endings on youtube Mystra seems like Mystra again - saving his soul if he's illithid, restoring his status as chosen if he requests, letting him know that romantic affair is possible and, as you say, letting him live his life as an ordinary human. It like all of those but I think it's odd that he gets an inferior ending when using the bomb in the upper city. To me it seems like video game logic - you are rewarded for doing more stuff - and not good story telling.
Of the unsatisfying endings to the game I do like Gale sacrifice best.
