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.
(..) It took Cedric ages to riddle it out. Almost all the bubbles were gone. Harry, tell me again. "Come seek us where our voices sound." The Black Lake, that's obvious. "An hour long you'll have to look." Again, obvious. Though, admittedly, potentially problematic. "Potentially problematic"? (..)2005 Harry Potter and the Goblet of Fire