A minor addition. I had a theory about it in another thread.
TL;DR: the resources of the team (maybe) were cut, so the had to use created assets in a way to make sense out of the story. The original intention with night elves and blood elves is covered in the blizzcon 2005 video.
[edit: while the execution of early times - Classic / TBC - is gnarly, it oddly enough feels mostly “in universe”, “in character” and simple ideas lead to a seemingly coherent world building. So, I’d early stories could’ve been presented better, but concepts IMO worked better than what we got in Cata+ time.
It’s still a mystery to me, what happened. Metzen is the same lead writer for Cata and W3, yet one of them is simple yet works well, and another is, sort of where it falls apart. But he was not even in the quest team afaia]
gl hf