Intent - mens rea in the law - is not about the intent to [commit insert crime here]. It is about the intent to do the thing that resulted in the crime. That is why if you get blackout drunk and drive through a crowd of kids, you get charged with manslaughter: you didn't intend to kill those kids, but you intended to get blackout drunk and drive, which resulted in the death of the kids.

Facebook absolutely would have criminal intent the same way kiwifarms would - in both cases, they intended to serve content from their users.