Austin has had a steady influx of people over the past few decades, but things have really gotten insane over the past couple years. To me it's been a lesson in what I call "hype-tipping points".
Don't get me wrong, there is a ton I really like about Austin: really strong job market with tons of tech jobs, lots of stuff to do outdoors most of the year (the lakes, hike-and-bike trail, etc.), investment in great public spaces (the downtown library is a masterclass in architecture and design, the relatively new boardwalk is great, etc.) But there is also a ton that's not great about Austin (e.g. horrible traffic with extremely limited public transit), and all-in-all I feel like it just kinda got "anointed" as the "cool" city by Elon Musk and friends to the point where it no longer deserves it's hype.
I mean, Austin metro is still relatively small/mid-sized, such that it just doesn't have any of the amenities of larger cities like NY/Chicago/SF when it comes to things like world-class theater, museums, sports teams, architecture, etc. Austin famously touted itself as "Live Music Capital of the World" and its "Keep Austin Weird" slogan, but the dramatic increase in cost-of-living has basically priced out many of the musicians and others that made it "weird".