To be fair, country artists have always been better about this than any other music genre. Also, they never stopped the old school methods of finding faces/voices and putting them together with the best songs and producers and musicians (studio and live). As much as Taylor gets her own writing credits she also has a lot of collaborations. It's also likely that she's only just starting to make her own decisions, but not these ones. She's got an excellent marketing machine supporting her, one that is setting her cues...not looking to her for advice on how to reach the audience. It's just that her team is listening to their tech-savvy members (presumably younger "hipper" folks) that have the foresight to see how modern social media and apps can be used to maximize exposure.
There's definitely a formula to it, but, as has happened during the history of popular music, it really has be the perfect artist/band at the perfect time or EVERYONE would be famous. I still wish it were happening to a far better artist. There are quite a few beautiful young women that can actually sing wonderfully, write infinitely better music, and are also stellar instrumentalists. SHEL is four sisters of amazing talent that write and play excellent music. Larkin Poe are two sisters that are on a similar level, but are growing towards a broader rock and pop sound after starting in bluegrass (while never being modern country). St. Vincent is endlessly better than Swift on every level for me, but she's got a vision for the art she wants to produce and isn't likely to veer towards various genres,
For me the biggest difference (the reason she's everywhere and my examples and others are unknown in comparison) is that Taylor is far more vanilla...bland. She's goes easier to listen to for the average passive music fan, the people that actually are hurtling her album toward multi-platinum by year's end. The same people that are getting sucked into buying her other albums since her people realized that having stream for free on Spotify would negatively affect the facade that is album sales figures. Yet at her level she should be making some decent/serious money off of sales.