Kingdom Hearts (2002) was the Castle of Illusion Starring Mickey Mouse (1990) of its decade, it took beloved characters, put them in a popular genre, and had great animation and sound to back it up.

Now take a minute and Google all the Mickey Mouse games of the 1990s, just the Illusions series alone had like six. Can you imagine if they had an overarching story trying to tie all those games together? And if that story was, say, created in the PS2 / PS3 era of making super-long JPRGs full of nonsense cutscenes?

Oh wait... right, Kingdom Hearts has sequels. And that's really the answer. Disney plus JRPG equals money, apparently, so they're just making ever-more of this stuff while making it up as they go-along. See also Star Wars (post-Disney).

When they get really lucky they hand a license to a tight team with a vision (Mandalorian) and get something good for their money, but the high budget stuff (Kingdom Hearts included) is basically doomed by its own success to be some conglomeration of nonsense.