And I didn't say that you said that. I said that I believe that the intense fixation upon Karena and her friends (by documentaries, podcasts, etc.) could have provided cover for MESO. Because from a murderer's perspective, it is hard to imagine a more ideal situation than to have so much attention focused on a person who isn't you. Frankly, if MESO had been a bit more careful about leaving his DNA at the scene, he would have almost certainly gotten away with this.
I've always wondered if the girls had any bleach or cleaning supplies in their apartment. If they did, then there is a real possibility that MESO could have destroyed vital evidence if he'd just been a bit smarter.
There is another case where a woman named Arpana Jinaga was murdered in her apartment, in a similar manner. But in that case, the killer was able to use chemicals he found in the apartment (bleach, motor oil) to destroy important forensic evidence. A man was eventually arrested, but he was acquitted at trial, and I'm not entirely sure that was even the right person.
The most important piece of evidence that MESO could have destroyed would've been the DNA from semen. If he'd even just gotten some bleach over that and destroyed it, then the rest of the DNA might have been possible to explain away as being a result of secondary transfer, and that might be reasonable doubt for a jury.
And of course, if he hadn't left the weird note, then his DNA wouldn't be on that and then there would be one less thing connecting him to this murder.