If you see talking heads with static/simple/blurred backgrounds from now on, assume it is fake. In the near future they will accompany realistic backgrounds and even less detectable fakes, we will have to assume all vids could be faked.
Technically videos could've been faked before but it would require a ton of effort and skill that no average person would have.
Courts already wouldn't generally approve random footage without clear provenance.
But that's nitpicking. It's good enough to fool someone not watching too closely. And the fact that the result is this good with a single photo is truly astonishing, we used to have to train models on thousands of photos for days only to end up with a worse result!