Bizarrely, unless I’m remembering wrong, the previous movie (Last Jedi) even set things up so that Rey would need a new lightsaber in Episode 9. Isn’t there a scene in Episode 8 where her lightsaber is ripped apart? You’d think that would nicely segue into a new, personalized lightsaber for Rey in Episode 9. But I guess not.
Concept art showed it being rebuilt as a dual-bladed staff, which would make far more sense.