Well, yes, of course there's a way to link it, by using examples where such a thing has occurred. If I had to bet, I'd bet that this particular perp, living in a town of about 25,000 people, had indeed been to the house before, especially after all that's been posted here regarding its status as a party house. IOW, a kind of statistical model.
There's no way to link the killings to voyeurism from the hill, either.
But both of these pieces of information are relevant. Potentially lots of relative strangers in the house, good views into the house from various angles, large same-age population living nearby, statistics about onset of some mental illnesses, etc. etc. It's all relevant and I do hope experts/police are weighing and evaluating these things and much more.
Unfortunately, the key is likely to be either "someone notices someone acting differently after the crime" and speaks up OR...
DNA. And then we'll know if that person had been there before or was known to the university student population or is part of it. Or is from out of town.
At this point, we don't even know if this is a spree type killer (probably not, I'd say) or which sex (I'm betting on male - but there's absolutely no reason the perp could not be female, IMO).