I would think blackmail works best when being used on things which are actually true. If someone wanted to blackmail me by sharing a fake photo of my cheating on my spouse I wouldn't cave for anything because I know I haven't so I feel confident I have enough other evidence to fight that claim. My location data, who is the "other woman", etc.?

On the flip side if I had commit some crime and someone made a deepfake of me doing that crime but they didn't actually have a legitimate photo, I might cave at that point since I would think it's a genuine photo and presumably they know even more about the incident.