So back when Pikmin 3 Deluxe was announced for the Switch people quickly took notice the Wii U original was delisted from the eShop. People assumed this was because Nintendo only wants people to buy the newest version of the game, and a similar thing happened with DKC Tropical Freeze back in 2018. Following the announcement that Super Mario 3D World is coming to Switch in 2021 people wondered if the same thing would happen with that game, but when people checked the eShop not only is 3D World still present, but Prikmin 3 is available on the Wii U eShop again (and presumably it was relisted in late August but no one noticed because lets be honest here who's still checking the Wii U eshop daily?).
Some speculation is Nintendo back peddled after receiving criticism from YouTubers like Arlo (Arlo's actually a brand ambassador for Nintendo), but at the same time a common reaction I'm seeing is "not sure why people were complaining so much over Nintendo delisting a version that barely any of the people complaining are gonna buy anyway because they either don't have or never had a Wii U to begin with."