The FBI investigates a small percentage of reports they get.

As has already been mentioned by others, the blackmail part might have gotten their attention. It is possible that is being investigated.

However, if that's true, Sarah and Victor are quite stupid to start this Onlyfans so quickly, if they really want to see this guy punished.

It is very hard to sell the "victim of invasion of privacy" narrative when you're selling hardcore porn videos of yourself on Onlyfans. I have to think the FBI will lose interest once they notice that Sarah/Victor parlayed the situation into selling pornographic videos of themselves for profit.

In general, it is difficult to build a criminal case around an adult content creator being blackmailed with sexual images they were voluntarily selling to strangers online. Sure, blackmail is always a crime, but it's just looked at differently at that point. It would be a much bigger deal if Sarah were NOT selling pics/vids of herself in sexual situations, and then some freak got a hold of them somehow (even if he was sent them voluntarily), and then used them to blackmail her. But once you get into selling your sex life to the public, it's really hard to push the narrative that someone was holding intimate videos over your head.

Maybe I'll end up wrong here and someone will get prosecuted, but I doubt it.