Austin being a tech boom city doesn't mean anything to the NBA or its players...unless you think the Spurs are going to manage to get some sponsorships from the Dells, Apples, or Teslas of the town.
If players want to go up to Austin to party or check out F1 or whatever, they can easily pop up here.
San Antonio already has an established fan base and culture in a city of more than 1.5 million people. You can't just expect to replicate that in Austin overnight, and you also shouldn't expect thousands of existing fans to make that "hour drive" 41 times a year. You seriously expecting to ask the fans to make that drive all the time, instead of the few players who may feel like checking out Austin occasionally?
I've been in Austin for a long time and can tell you that people are lukewarm on the Spurs. , they basically have to give away tickets to the Austin Spurs games just to get people in there.
Also, Moody Center is significantly smaller than AT&T and the parking situation downtown is a nightmare, so I wouldn't act like they have an arena just ready to go up here.
Don't get me wrong, I would love if I didn't have to drive down to SA for Spurs games...but bailing to Austin is just flushing their history down the toilet and spitting in the face of the city and fans who built them.