From the material posted it seems that this is basically a high-tech, convincing version of those late-night sketches where they have a fake version of their mouths moving; it doesn't actually solve the audio problem.
would be pretty easy to use an impersonator or something like lyrebird.ai to create the audio.
Yes but you can also track down the original video to prove something is fake. In order to have something truly convincing you need a video of Obama (or anyone else) that no one else has.