Because, Cheek to Cheek appeals to an older demographic who dont use Google.
The sales of 550k outselling massive popstars such as Ariana, Iggy, Nicki, Selena, Demi and even Britney Spears shows that she is still very relevent in the music scene.
I assume you think 2007 was a good thing for her career but if you look at the graphic, she's below Gaga, she might have been above her during S&S but that's all.
oh well not everyone can have a long career as a pop star
the average POp star life-span is 5 years
Madonna being one of the few exceptions with a 30+ year career
oh well not everyone can have a long career as a pop star