yeah bro, you phrased it all perfectly. Here's why the frat thing, and a lot of other theories are not valid, not just here but in a lot of cases that gain rampant speculation:
There is NO available actual evidence that points to them. None. It's a theory created out of entirely speculation, which is not how cases are solved. They are solved by following and interpreting the evidence. You can create a theory that the teachers at the college killed the kids, largely the same way the frats are implicated.
The source is random, not credible ,reddit reports, that follow a narrative of shock value, and "they are going to get away with it".
Third, the criminal psychology doesn't track. Frat guys can be lots of things. They can be drunks, they can be rapists, they can be great guys, and those things all at the same time. They can be great students and whatever to. But, they aren't born killers, this isn't a group like ex military, or a group of dudes just out of the pen. There is a certain level of vioence that comes from a group of men that is built on rituals, and male bonding, and competition, sure, but the idea that they killed 4 people in cold blood, is unlikely, to say the least. This is one killer. I've read dozens of books on these kinds of things, it's one killer.
So, 2, or three, much less 4, all banding together to cut up 4 women in a drunken rage? It's just not the way things work. Maybe, a beating or an accidental killing, on site, certainly rapes, can happen like that. But, organizing, while drunk, driving to the house, in the middle of the night, and stabbing four of their peers to death, over what? It's POSSIBLE, sure, but there is nothing to suggest that is what happened, as of now.