So why did they give Bordeaux a safe seat but not McBath? I guess the Republican logic is that they don't like having a black woman represent a white traditionally Republican district like GA-06. Whereas at least Bordeaux is white, so from their perspective she is more tolerable. But if voters in GA-06 get too used to voting for McBath, next thing you know they'll be voting for Stacey Abrams as well, and can't have all those black women running around with so much power.
It doesn't fit with your narrative, but it could just be that Cobb is less Democratic than Gwinnett, isn't trending quite as fast, and is more the sort of place where you could argue that the trends were Trump-specific (seeing more downballot strength).
