Wario probably crunched the devs to get it there.
http://www.nintendoworldreport.com/news/58132/warioware-get-it-together-demo-available
The next first party release for Switch now has a demo.
A demo for WarioWare: Get It Together! can now be downloaded from the eShop in North America. Nintendo's announcement has confirmed a "selection of minigames", but was not specific on how many that entails.
The demo checks in at 206MB.
