The video wasn't new. It's almost 2 years old.
It's hard to find raw video of it but it is easily available to find on YouTube through the nunber of DEBOONKED videos on it.
Essentially what happened:
They reported a toilet leak or pipe break in Atlanta, GA (that was so bad, it caused Detroit, MI, Milwalkee, WI, and Philly, PA to stop counting votes) to shoo the Republican poll watchers away. When the "evil MAGAts" were gone, they pulled out suitcases of ballots hidden from underneath the tables and continued to count them until they won to "save democracy".
Were the ballots fraudulent? No one knows because no one checked. They just recounted the same things without checking them.
Was it illegal? Yes, you need both parties present to count ballots.
Does it matter now? In a mitigation sense, nothing can be done now besides preventing it in the future obviously, but even 40% of Democrats in Georgia think the election was stolen there. It means a major peeling of support on the issue.