Mix of one of the largest flagship universities in the United States, state government of second largest state in the country, a big time music scene, and a lots of tech industries.
Nashville also combines a lot of those things and isn't nearly as liberal as Austin (less Democratic despite also being much less white), so I don't think that fully explains Austin's liberalism (actually, wouldn't the state capital of a conservative state even move it to the right).
Vanderbilt is tiny compared to UT-Austin. And country music is a wee bit more conservative than Austin's indie music scene.
