I agree with you. I have a hard time reconciling the fact that all were likely asleep when stabbed. I would think that if it were personal against someone, the killer would want that person to know who it was that did it…the killer would want that person to know that the killer “won” or that the victim “paid the price” for some perceived wrong. I do get that sometimes in murders that are personal, the killer’s goal is to just end the victim’s life and it doesn’t matter if the victim knew it was happening, so I could see it being personal and the victim still being asleep. However, I can’t see how someone would want the lives of four people to just be ended if it was personal, unless the killer perceived that all four were his targets from the beginning. This probably makes no sense.
TL;DR, I think if all 4 were asleep when attacked, there’s a good possibility it was some psycho that just decided to enter a house one night and kill a bunch of people.