>>30920929Since we're already mired in headcanon in this thread anyway:
I just assumed the Elite 4 were a more-or-less "permanent" job position like the gym leaders, and they're replaced when they retire or whatever. They can't function the same way as the champion, where whoever the most recent winner is gets the spot, because they get challenged a lot and it doesn't look like their spots are in flux from that.
So maybe Agatha is dead (since she's the only one of the four without an explanation for her disappearance), or maybe she just decided she was too old for this shit and retired. Either way the people in charge of the league (the current champion? Maybe a board or something?) stuck someone else in her place.