It's not surprising that Georgia turned blue, it's been happening for years now. Remember when Stacey Abrams almost won there? Atlanta has been liberal for a while because it's a big city, and there are a few other pockets of blue, like the cities of Savannah, Augusta and Columbus as well as Athens where the University of Georgia is and the "Black Belt" that runs through the rural center of the state which has lower population but a higher proportion of Black people. What is new is that metro Atlanta's population is outvoting the rural parts of the state. Part of that is because more people are just moving there from other cities and countries, and those people don't identify at all with the "country" parts of Georgia. As for why it flipped late, I'd guess it's because the results came from Fulton County. Fulton County is home to Atlanta. The suburbs in the north are rich and white and those in the south are poorer and Blacker. If you look at any election results for the last ten years, you'll see Fulton County is far and away the last in the state to have results. Part of that is because they have so much population. Part of it is because there are precincts in the north and south that have a ways to travel to Atlanta to deliver their results before they can be counted. Part of it is because the elections department can't tell its ass from its elbow. This year, State Farm Arena, where they were doing their counting, apparently had a water pip burst on election night, which slowed down counting more. Of course, I don't expect anyone on the right to take any of this into account and instead they will scream about conspiracy, even though the governor is a Republican and a huge Trump fan who has been accused of stealing the election from Stacey Abrams while he was secretary of state, and the current secretary is also a hardline Republican. If they were going to steal the election, it sure as shit wouldn't be for Joe Biden.