I don't think I have ever knowingly heard a Taylor Swift song. If I have heard one on the rare occasions when I can't avoid being inflicted with daytime radio then it went in one ear and out the other. I don't believe I have ever heard anything by Katy Perry, Beyoncé, Ariana Grande or Lady Gaga either (even though I am perfectly well aware of them), and it's probably 30 years or more since Madonna did anything that impinged on my consciousness. (I do have Holiday and Into the Groove on 12" vinyl so I really am a pop-tart at heart.) What am I trying to say with this? Perhaps that the insidious reach of popular culture is not all-pervasive and can be selectively avoided if you try hard enough.
To those who seek reasons as to why Taylor Swift is so popular, I doubt there is any easy answer. Ascribing her success to talent and hard work seems to me the least likely explanation. There are hordes of talented and hard working individuals from all walks of life who have neither achieved success, fame nor wealth. On the contrary, talent or even any enviable personal quality seems singularly lacking in the bulk of the rich and famous.
The cynical explanation is that shit always floats to the top. But that's a bit glib. And there are definitely examples of popular and successful artists who posess both creative talent and artistic worth.
A more likely explanation is simply luck, chance, serendipity, a random fluctuation of the space-time continuum. Just like the proverbial butterfly flapping its wings in Kabul can cause a hurricane in Kansas the gusts and gales of popular taste can arbitrarily propel some random nonentity into the stratosphere of fame and fortune for no apparent reason.
Personally, I'm a big believer in the meme theory of cultural evolution as proposed by Richard Dawkins in the final chapter of The Selfish Gene in the mid 70s and later expanded upon by the likes of Sue Blackmore and Dan Dennett. Just as a successful gene is a sequence of nucleotides that is good at getting copied by the machinery of DNA replication, a successful meme is a thought, an idea or symbol that's good at getting copied though human social interaction, e.g. imitation.
Taylor Swift is a successful meme, or perhaps rather a collection of memes, that simply happens to be successful in infesting the collective grey-matter of humanity ...