Various forms of moving image manipulation has been taking place since the invention of moving images. As with any technology, it gets easier to do as it disseminates out to the general public. The question, as always, is "why would anybody bother."
You're hearing about this now as "deepfakes" because it's a consumer-level technology that applies a consumer-level want at a consumer-level price. In other words, "I want to add to the burgeoning constellation of Emma Watson anal deepfakes and am willing to spend an hour at the computer for something I will never be paid for, but which will allow me and my hairy-handed brethren to dream more easily." The counter-case is a journalist who enjoys putting his wife's face on Anne Hathaway. You'll notice that
A) no one is paying him to do this
B) he didn't ask his wife if she wanted this.
That's important: yeah it's kinda fun to do stuff like that but as gifts go...
Beyond just pure fun, I can only imagine how people will start turning this tech into business ideas. Fashion will be huge (what would I look like with this kind of hair, this kind of dress…), fitness could be interesting (do I look good with muscles, will I really look better skinny), travel (this is you standing on a beach is going to be quite convincing). It’ll bring advertising to a whole new level. No need to imagine what if, they’ll tell you what your “better” life will look like! And it’ll be hard to get that picture out of your head…
This is one of those crafts where to the creator, it looks cute. To the victim, it looks like that head from The Thing that grew spider legs and crawled around. The Uncanny Valley is one thing when it's a stranger. When it's you?
The technology to do this has been around for a long time in the professional sphere, but there hasn't been any call for it... unless you're talking about "shit, we need Grand Moff Tarkin in this scene and Peter Cushing has been dead for fifteen years." You'll note that audiences were... impressed? by that trick because none of them really remembered Grand Moff Tarkin but as soon as they resurrected Carrie Fisher results were a lot more mixed.
Fundamentally? We're talking about the value of authenticity in a sphere where artificiality is easily accomplished. And it's been twenty years since DeBeers started slapping serial numbers on their "real" diamonds because the fakes were chemically and physically identical and they still own the diamond market.
Here's a Scientific American article about using fractals and machine learning to spot a fake Pollock... from eleven years ago.