I have a theory.
Super Smash Bros 64 featured a lot of characters that originated from the SNES era of games. This includes the likes of Ness and Captain Falcon.
Melee featured a lot of iconography from the N64 era. The Ocarina of Time versions of Link, Zelda and Ganondorf.
For WiiU/3DS featured iconography from the Wii era. Such as Rosalina, and Little Mac.
(I should do a full timeline of this)
My point is that a Smash game always seems to borrow it’s characters and iconography from the previous console generation. And as such a lot of Wii U era characters will be part of this roster. Sakurai even soft confirms this by admitting that his project plan was completed in 2015. So now you may be thinking. “The WiiU was a commercial failure. What characters could they pull from that era?” I don’t know about you, but I could name 100.