People have been able to do this via video editing and audio manipulation for a while now and much better at that than state of the art deepfakes, and yet this

People have been able to do this via video editing and audio manipulation for a while now and much better at that than state of the art deepfakes, and yet this isn't a problem despite the huge incentives you imply that would motivate very powerful, wealthy groups with the means to easily pull it off. Video evidence is still a thing, too. Criminalizing making fake videos of any kind is extreme authoritarian behavior and libel is already punished by law everywhere I know. If you don't like how libel is punished in your jurisdiction that is another matter, but if you want to get some ideas on how to make them harsher just get a list of countries and filter by dictatorships and you're bound to find examples that take libel and its definition very seriously.