1) Why is it surprising that it is so wealthy? I have always thought of Nashville as a fairly affluent city...
2) Why is it REMOTELY surprising that it is so Republican?? Lol. It is a wealthy and white county in a moderate-but-not-huge metro in the American South ... those areas are nearly all Republican, and the ones that aren't are centered around very diverse and much larger metros like Atlanta.
It's an oddity in the sense that among the top 20 wealthiest counties, only 2 are GOP-leaning and among them is Williamson.