>>719237730
>how did they do it
Mostly separate the entire story from the main one, an isekai that separates us from what feels safe and well threaded, then create actual character for the already existing characters.
Explain the threat facing the world, and our world, very clearly. Show the consequences of what is happening, constantly. Have everything in the story revolve around that threat of the Light. Even the new major characters are tied to it.
Then spend time to understand the villain, all the major villains so far, and the inner workings of the world. But have them still feel godlike, ancient, and somewhat out of reach.
Wrap it all in satisfying and well paced emotional and story rewards.

Endwalker sloppified what was set up by rushing so much, and changing the entire story halfway through. Sure pays to mush two expansions into one.