Originally Posted by
Super Dickmann
The thing is, as I've explained to others in this thread, Tyrande showing up empowered by the goddess now may well actually serve to improve the feelings of betrayal people like Sira might have. Their goddess did fuck all when their people were exterminated and Tyrande wasn't even present, but now Tyrande is the vessel of her revenge after the battle's basically already been lost. Elune has granted Tyrande protection enough to resist the val'kyr, as she does when Brynja tries to bind her, but she did nothing of the sort for the now undead night elves ensuring their souls are damned. These are again thing that wouldn't crop up to a fully rational mind, but for someone with as much massive trauma they'd be big sticking points, especially with how undeath numbs your positive feelings and buffs up negative ones.
On top of that, Elune hasn't actually bailed the night elves as a whole out all that often. As night elf fans themselves point out and as is a meme in the community ,the night elves have gone from one loss to another declining from a faction superior to both Horde and Alliance in WC3 to losing their ancestral homelands and being driven to near extinction in BFA. If their goddess cared that much, surely she would've stopped that, goes the narrative for the risen dark rangers.
Finally, Delaryn, from what we see, doesn't announce her loyalty or even attack Tyrande. She repeats what she thought about while dying and seeing Teldrassil go up in flames and then goes silent and catatonic after she's back in camp. Her story will clearly carry on from there and given how the narrative is, as you are pointing out, going in the direction of Sylvanas' defeat, it's clear that she'll in some way be involved in rebuffing her ideologically.
None of this is to say the motivation is amazing, it's shit and borderline ridiculous, but it has enough legs to stand on for non-characters like the risen rangers, who are clearly a skewed sample from how the Val'kyr browses for willing souls, or Sira, who has no personality traits to speak of.