There has been plenty of hearsay (and actual evidence to look at in 2018 even though Kemp did win that time), about people in the Atlanta suburbs just not liking a Trump or Kemp type Republican. Enough that I knew that the results at the very least were going to be closer (I did not expect a flip, though), so please forgive me for being unsurprised that they were.
The percentages in the Atlanta area counties that went blue both times:
2018:
Fulton: 72.3%
DeKalb: 83.5%
Douglas: 59.8%
Clayton: 87.8%
Henry: 57.3%
Rockdale: 67.5%
Newton: 54.3%
Cobb: 54.1%
Gwinnett: 56.6%
2020:
Fulton: 72.6%
DeKalb: 83.1%
Douglas: 62%
Clayton: 85%
Henry: 59.7%
Rockdale: 69.9%
Newton: 54.9%
Cobb: 56.3%
Gwinnett: 58.4%
These results are largely not that crazy given the things that I’ve heard. Some of them track very closely to 2018, and others were fairly recent GOP holds that have been lost at least for now because of a wave of changing demographics in the area, and because of RINOs that really can’t stand Trump/Kemp to the point where they can’t hold their nose about them to try to “own the libs” or w/e (the fairly recent GOP holds that have been recently lost are Cobb/Gwinnett). The ones that don’t fall into this description that ended up having a fairly significant shift (around 2% or higher) are:
Douglas
Rockdale
Henry
Clayton (with a shift TO Republican, but still very heavily blue)
Maybe Dems tried to cheat in Douglas/Rockdale/Henry, and maybe you had black people who were discouraged in Clayton County about what’s been going on or even had their voices suppressed? Because it’s not like Georgia’s history is squeaky clean about voter suppression (although the SOS that’s there now has suddenly started to try his best to help out, as he did initially also partake in what Kemp did allegedly).
But either way, although it's turned out to be a very dumb move by him, there was a reason that Kemp appointed Loeffler instead of Collins for senate. He knew that the suburban people were turned off by him and Trump, and appointing Loeffler was his attempt to try to appeal to them again (especially the suburban woman). It's backfired hilariously, but the smoke has long been there here, even if Trump had won the state.