Even if the DiC shows or LA movie didn't exist, I'd still think Isekai-ing the Mario movie would be necessary - mostly because the Mario universe is really weird in a way very few other fictional worlds are, and using an outsider protagonist makes exposition a whole lot easier for newcomers, especially kids. Not to mention that Mario as a character design is kinda ill-fit for the universe he's in, so may as well just play into that.
