Georgia is one of the most highly educated states in the South and education is highly predictive of election outcomes.
The Presidential election outcomes in the other 46 U.S. states and in the District of Columbia can be explained entirely by the extent to which their citizens are highly educated.
There are four outlier states that don't fit this trend perfectly. Utah (Trump + 21) and Kansas (Trump + 15.6) are more educated than their fellow red states. Nevada (Biden + 1.6) and Wisconsin (Biden + 0.6) are less educated than their fellow blue states.
There are also explanations for these outliers. Utah is an outlier because it is so religious even though it is also quite urban and highly educated. Nevada is an outlier primarily because it is highly urbanized (the vast majority of the population of Nevada lives in the Las Vegas or Reno metropolitan areas). Kansas is far more rural than most states that are so highly educated. Wisconsin is right on the brink by a variety of measures and resulted in a very narrow win for Biden this year.
The strong correlation of education and partisan preference is relatively new. Until fairly recently, college educated white voters tended to vote Republican, and non-college educated white voters tended to vote Democratic. But, in the last few election cycles, college educated white voters have shifted decisively to the Democratic party. Georgia, which has a high percentage of college educated white voters relative to most other historically red states, has shifted with this trend.
Georgia has also gradually become more urbanized and more educated (in part due to migration from the North to economically booming greater Atlanta).
It isn't entirely clear if the very strong link between education and partisan preference is specific to the Trump era, or if it is a long term trend. Republicans have been gaining ground with non-college educated whites all of the way back to the Reagan Democrats. But the Democratic party's dramatic gains among college educated voters didn't really materialize until 2016 when Trump faced Hillary Clinton.