Popularity is the state of being popular. When people like you.
Popularity, therefore, is both a two-edged sword and a not-very-good measure of quality.
Remember, kids, just because all your friends are doing something doesn't mean you have to as well! Unless they're eating their vegetables, getting their vaccinations, and doing their homework. Then you should copy them. But if they're jumping off bridges, writing badfic, or fangirling sparkly vampires, then feel free to ignore them.