Difference between scene

I’ve been working on one scene of a game. I’d like to make another level, that has much in common with the first, but not everything. So I duplicated the first scene called “DemoScene”. In my project, DemoScene is the first level. DemoScene1 is the second level. Both of them are same and added to Project Setting.
However, view is different in spite of the fact that they are same.
There was not any changes after duplicating. Why did they look like different?
DemoScene (level 1):

DemoScene1 (level 2):

I think I’ve had this problem in the past. I solved it by going to Window → Lighting. In the Lightmaps tab I unchecked “auto” and clicked build. This will build light maps for the whole scene (not just one light).

Can anyone shed some light on why this works, I don’t know.