Most people don't know that MG owns most of the industry. They've done a really good job making sure no one looks behind the curtain.
They’ve even achieved regulatory capture. The UK has a law coming into effect that will require porn sites to require ID-based age verification; MindGeek is naturally the primary company developing such a system: AgeID.
First, they have tons of verified accounts with revshare ala YouTube monetization at the same or better rates / view.
Second, MindGeek owns all the tube sites and all the premium sites. Them and advertising networks like TrafficJunky are the equivalent Google Ads for the adult industry.
The premium sites are heavily affiliate marketed to the tune of mid $xx per free signup, or $x per email, or massive mid xx% rev share for life of a paid signup.
MindGeek and the premium sites give out all the content or upload themselves the content on the tube sites.
Furthermore most videos and metadata is syndicated through standard feeds so all the tube sites have the same stuff.
Just standard funnel / marketing / sales process.
I am not making judgement on any actually illegal content that might be there or actually copyrighted stuff; but really it seems the vast majority of it is allowed to be there.