Because Mario Multiverse is a fan-made project and not an official Nintendo product, it is not available on mainstream storefronts like Steam or the Epic Games Store.
Forget a simple Bowser rescue mission. Mario Multiverse takes the classic 2D platforming of the original Super Mario Bros and smashes it together with mechanics from Super Mario 64 , Sunshine , and even Galaxy . Mario Multiverse Super Fanmade Mario Bros Download Pc