The only illegal sexual activity Skopek detailed involved an unnamed computer technician raping him. Skopek doesn't provide any smoking gun for Singer. There's nothing illegal about being a sleazy, decadent and empty person. Singer can host all the ten person, drug-fueled, twink orgies he wants. Provided everyone is at least 18 and consenting, there's nothing wrong with it.
I don't want to oversell any one story as the smoking gun that'll finally, definitely bring down Singer (especially as I have a feeling there'll be a drip-drip-drip pattern of stories on Singer), but I think you might actually be underselling it. Yes, you're right that there's nothing illegal described here, but there is definitely a pattern established here of predatory behavior with much younger men, many of them barely legal.