One of the largest issues is jurisdictional issues. These internet sites are global, but most law enforcement have fairly restrained jurisdictions. A victim may go to their local police, but the local police then have to interact with agencies potentially all over the globe to actually build a case, make an arrest, etc. Which isn't to say they don't try, but it can be very difficult and take a very long time.

Even if you can track down someone's ex-boyfriend (likely to be more local) and charge them, once the video is out on the Internet, random people all over the globe can continue to share and distribute it. And large scale video platforms have little desire to put meaningful controls on uploading videos as it would negatively impact their ad revenue. Furthermore, these platforms can claim that they didn't upload it, a user did, so they shouldn't be held responsible.