I’m from East Cobb and live here currently. There’s been a big change from 2000, starting in 2016. 2020 highlighted the shift.[1] I don’t think it’s race related if I look at the demographic changes in the past few censuses.

East Cobb has always been more conservative and they have a senior population who’s not changing views.

[1] https://www.11alive.com/amp/article/news/politics/elections/...