Does anyone have real world experience monetizing porn sites on a such a large scale? I am not familiar with the business aspects of it. Is it driven through affiliate? Direct advertising? Something else?
It depends on the kind of business you are. If you are actually a producer of porn (bang bros, naughty america, kink, etc.) you sell subscriptions or "points" packages for pay-per-view/live streaming. To get those subscriptions you use just about every method out there and continue to try since the way traffic is driven to porn sites changes every year. It's a mix of affiliate traffic with a different mix of programs like revenue sharing, pay-per-signup, etc. and then you throw in a mix of other direct ad programs like ad words.
One of the difficult parts of being in the porn business, aside from the difficulty in getting a bank that will actually process your transactions, is that the way traffic is driven to your business changes annually. The affiliates bear the brunt of that, though, but you pay them about 50% of the revenue they bring in for that so it is costly. But you're always trying to find ways to bring in traffic yourself since you don't like giving up 50% of your revenue to an affiliate.
You have two options, outright selling the ad spaces (like what the PornHub network does) or attempt to sell memberships at other sites for commission. Not easy.