This doesn’t bother me that much because evidence isn’t required to convince millions of people that a lie is true. We already know this. Why make fake evidence that could be debunked when you can just have no evidence instead?
Instead, what may be a cause for concern is simply the installation of doubt in an otherwise reasonable person because of the perceived validity of contrived evidence. Not so much that it becomes a sincerely held belief, but but just enough that it paralyzes action and encourages indifference due to ambiguity.
Often the lack of evidence is the proof of whatever is being peddled. "No evidence for $foo? OF COURSE NOT! Because 'they' scrubbed it so you wouldn't be any wiser! But I have the 'truth' here... just sign up for my newsletter..."
This seems like an assumption too. I know there are instances like you’ve described but they’re not absolute nor universal and I accounted for that in my original comment.
Think about how many people believe in Jesus without any of that physical evidence.
If anything, the physical evidence turns most people off. And I'd argue that most Bigfooters don't even believe in the physical evidence, but use it as a tool to hopelessly attempt to convince other people to believe in what they already believe is true.
For some reason many people react to learning about deep fakes' potential with huge concern as if photos and video used to be infallible and it's suddenly being overturned when this really hasn't been the case.