I’m actually amazed online sleuths don’t need any information whatsoever regarding the whereabouts or happenings of E/X that night (morning of) at Sigma Chi and other possible locations to determine their final product.
IMO, the lack of internet sleuthing on both M and X is bizarre. I think it's unlikely E was the "target" and the other three girls were just collateral damage, so I get the lack of focus on him. Although it could be someone connected to E who targeted one or more of the girls, so sleuthing him should also be a priority. But both M and X or all three of the girls combined could be the one(s) targeted.
I get that we have the most info about K because of her family's media approach, but that doesn't mean much in terms of who and what to investigate.