If you take a close look at that district you'll see why it's shouldn't have been a Republican walk-through at all. In fact, Ossoff (if Ossoff was someone other than an unmarried, 30 year old filmmaker who didn't live in the district) should have won in a landslide. That district has morphed over the last several years from staunch right to majority left. It is the most well-educated district in the country, a demographic that Trump has not done well with at all. Hillary lost last that district by 1 percentage point. If she'd had a message, other than "Trump's evil," she would have won that district, and likely the election, by the margin she and the media thought she would.
People point to the fact that the new Health and Human Services secretary, Tom Price, won that seat by 20, ostensibly to imply that the district is heavily Republican and a Democrat is a way long shot to begin with. But what people fail to take into account is that Tom Price didn't run against anybody. Some Democrat got their name on the ballot and didn't campaign, didn't raise any money to campaign, didn't even try. You'd be hard pressed to even find a picture of Tom Price's opponent in that race. The story from that one isn't that Tom Price won in a 20 point landslide, but rather that Tom Price ran against nobody and only managed to win by 20 points. That's only marginally better than eeking out a win over the dead guy. If Price had had a viable opponent, he'd have lost yooge.
Democrats wanted GA06 bad, bad, bad, and they went all in to get it. And they should have won it. But they put forth the wrong candidate, and hitched him to the same "not trump" narrative that doomed Hillary, and SC, Kansas and Montana, and as we've seen time and time again will only get you 46-48% at the polls. You need a message.
It also didn't help that Ossoff ran as a liberal Democrat and then in the last 3 weeks or so of the campaign he changed his stance to that of more of a fiscal conservative, and people saw that as him saying whatever it takes to get elected, a la Hillary, rather than being true to his principles.
But that's what the Dems spent their money on. And they made it 100% a referendum in Trump. Except, of course, the instant Ossoff lost, it suddenly had nothing to do with Trump.