As for the mechanics of "framing" him, it would be very simple. Those specific murders might have been chosen because they allowed the widest possible number of suspects and there had never been a prime suspect. Once those specific murders were chosen, the person arranging the set up would simply look at arrests from that time period that involved any sort of violence, in this case an assault, and monitor the news for a hook to hang the "frame" on. They could have had hundreds of potential patsies. One day Bittrollf's brother gets charged with beating his wife or whatever they review the context, make a final examination of the suspect, go over the case files and purge anything that doesn't fit.
Just speculation but it fits better for me than the official version, unless somebody can give some weight to the dna evidence beyond "a bunch of cops and their buddies say so".
I can't prove it didn't happen that way but will say it takes quite a feat of mental gymnastics just to hold the theory together. Things do tend to look fishy when all you look for is fish, and with persistence and the right type of bait some can't resist latching right on.
Some other questions if somebody who followed the trial knows.
1) Was Bittrolff's position ever that he did have sex with either or any victim?
2) He seems to have switched from an out of the loop local lawyer to a high priced legal team with extensive connections to the local establishment. Who paid for that lawyer?
He initially denied, maybe he still does. It sounds like he knew they had him dead to rights but even with the evidence presented still organised enough to deny ever seeing the two victims. He would take his chances with a jury. We kind of expected a little more hoopla when the trial started but as marble documented there wasn't much media attention, which of course fueled our speculation. I don't know how that lawyer got brought in but I could see those that believe in his innocence could cobble together a good defense. As it turned out no defense is sufficient when a jury decides the evidence against you is beyond reasonable doubt.
LE would've had the unknown sample that matched from the two victims on their books for all these years as well as in codis. There it lay until the push came to identify this known serial killer that was operating twenty years earlier. speculation is the push came because of the lack of evidence in the ocean parkway cases. so they went all in on another known SK case in the area and within a reasonable time proximity in which dna was on file looking for a link to more current cases. Apparently no link exists. However this came about, the fact that they got his azz for what they could prove he did is a good thing.