The same way trashy boyband slop sells everywhere else: they have a different taste than you and judge music differently.

With boy bands like The Backstreet Boys or the Beatles, they don't go for some artsy music. All they need are songs that get stuck in your head and some pretty people singing them to get little girls/boys fawning over them.

And fun fact: their opinion is just as valid as yours. Because there is nothing as subjective as music.