Her reasons for leaving were 'obvious'. = It's 'obvious' why she left.
You are stating 'the obvious'. Tell me something I don't already know.
Her doctor immediately noticed the 'obvious' signs of the disease.
(..) - Why not? Well, I didn't think it was necessary. She was pretty well beat up. Somethin' sure happened. It was obvious. Now, Sheriff, you say that she was mighty beat up. In what way? Well, she was beaten around the head. There were bruises (..)1962 To Kill a Mockingbird