I'll be quite honest, the lore/story for a map or the transition to-and-from matters little to the playerbase at large compared to the story they create themselves by simply role-playing on the server.
I remember a lot of storylines, events and locations designed by staff that worked on some story going to waste as nobody but a select few of their friends bothered to unearth in previous maps. I've heard stories about Anthos, for instance; how half the builds got abandoned because players were far more invested in their own inter-personal plotlines and nation/faction conflict; or Asulon, even, where it took the map becoming corrupted after a series of attacks on the server itself for the large majority of the playerbase to find out there was even a world story/questline going on behind the scenes.
As far as what the world may need for a story to develop, I can think of ancient landmarks and ruins sprinkled throughout in a way that makes sense from a geopolitical standpoint. Interesting sites people can work with directly or narratively. Give us gorgeous vistas and interesting geography. Design a proper sandbox, and approach it as you would a hex-crawl TTRPG. Avoid staff-made antagonists and all the large-scale, over-arching nonsense that comes with them. They often do nothing but annoy players as it gets in the way of the stories they want to tell. If it fails to be interesting to them or align with the popular trends at the time, the entire project will have gone to waste. Besides, if we really want an antagonist force, we can come up with one, or become our very own.
The map story should be defined and written by the players in an emergent way. All you need to do is provide us with fertile soil. We'll handle the rest as we go about our daily lives on the server.