Nintendo has shared their own internal interview with Luigi's Mansion 3 Producer Mr. Tanabe and Supervisor Mr. Ikebata, which gives some insight into the game's setting, as well as the team's thoughts on Luigi. Check out those snippets

How the hotel setting was decided on

T: With a hotel, it's easy to envision how rooms are structured: they are lined up above, below, and beside each other. For instance, if you are in room 102, you would immediately know that room 202 was directly above you.
In the beginning, we thought about focusing on puzzles that happened in rooms that were just next to each other, side by side. But by having rooms above and below, it kind of adds to the amount of stuff that we can do from a puzzle perspective. For example, if you see water dripping down from the floor above, the player will understand that they need to explore the room above them. It can be difficult to visualize a building's layout in your head, so we felt the structure of a hotel would be easy to understand.
I: The atmosphere completely changes when you progress from floor to floor, so we've prepared various puzzles that match their atmospheres. By making each floor a different atmosphere, I believe we've been able to create puzzles with more depth.
On what makes Luigi...Luigi!

T: If Mario represents what most people think of as a "hero," I think Luigi represents the "underdog." I think his unreliable persona is also Luigi's ch...