PornHub has rules against this kind of content, but since all their content is user uploaded (and so much of it is user uploaded), stuff inevitably slips through. That doesn't mean the site is facilitating sex trafficking.

Additionally, they described GirlsDoPorn as a "partner site", which is misleading at best. Any porn company can sign up for an account and pay to have their trailers promoted. I remember seeing some of those trailers, and their stuff was all fairly vanilla. What it turned out was that behind the scenes some of the girls were being deceived. Apparently they thought they were shooting private porn films that were sold to rich clients and never put on the internet, when in reality GirlsDoPorn was a hugely popular site and so these young women would be horrified to find out they were being seen by potentially millions of people. There was also talk of coercion where some would fly out to shoot but get cold feet and the producers would threaten to make them pay for the flight and hotel among other things. Also I think they would sometimes pay them less than was initially agreed upon.

There are a bunch of articles about the GirlsDoPorn situation if you want the details, I don't remember it all that well. But at any rate, I don't really see how any of this is supposed to make PornHub guilty of sex trafficking when there was no way they could have been aware of any of this.