Simple, she's a clean cut artist that who's music is relatable (though the theme is the most generic) She did one of the most popular genres for nearly a decade & now does THE most popular genre & she's never sexual. She's one of the least offensive artists, ever. If she ever takes a risk she'd probably flop, but don't fix what isn't broken.
She did country which is the best selling music genre
And she's kind, white and cute, people eat that up
Let's not forget she's tall, blonde and pretty and has cute relatable songs aimed at teenagers - girls more on the specific side. She's kid-friendly too so the kids' parents and kids love her. She's BFF with every cool celebrity (minus Perry) and has your typical awkward cool quirky personality. Let's not forget she's very close to her fans and has social media to connect with to them with.