A month before Pokemon Sun and Moon launched in 2016, Eurogamer told the world Game Freak was working on a project code-named Pokemon Stars which is essentially Pokemon Sun and Moon on Nintendo Switch.
Fast forward to 2017 and we all know that didn’t turn out to be true, as Pokemon Ultra Sun and Ultra Moon were released on Nintendo 3DS instead. Eurogamer explained in a report there was no single reason why the project was abandoned, but a few points do stick out.
First, Nintendo started believing the Switch would turn out to be a success so they didn’t need a Pokemon RPG out on it in 2017, as they are already other big hitters like Super Mario Odyssey. Second, Nintendo needed something to prop up the 3DS for the holiday season for its audience, thus the gears were changed to Pokemon Ultra Sun and Ultra Moon.
The last theory was Pokemon Stars wouldn’t have been a true and huge leap from Sun and Moon to the Switch. After all, a straightforward port to the Switch wouldn’t have been as exciting as a fresh and new Pokemon game taking advantage of the Switch’s full power. Thus Eurogamer believes the course was switched from Stars to Ultra Sun and Ultra Moon “late last year”.