I think it was strategic. In this sense: he was tried for the SA charges because they believed they would convict him. I don't think we've heard from jurors but I suspect that, if we had, they wouldn't have said they believe CB is innocent, just that they didn't feel the Prosecution cleared BARD, and therefore, they were required to find him 'not guilty'.
LE is not opening up a new investigation, like there's a different assailant out there. The Prosecution failed.
MM is a no-body case. That has gone unsolved for years but IMO finally had evidence linking CB but now it appears it's evidence questionably attained and easily suppressed. Still it might be of such clear and convincing truth that it looks CB AND it confirms death. Enough to satisfy those in the innermost circle but not enough for BARD.
Given that CB was already incarcerated and already heading to trial over the SA, it gave LE TIME to continue investigating CB for MM, the biggest piece of evidence to gather -- MM's remains or at least more physical evidence, from that campsite.
But the SA trial collapsed, MM was not found, the factory evidence is not usable, and CB is about to be released, having served his current sentence.
As I see it, CB did commit these crimes. LE is hamstrung to prove it however. Knowing it beyond a doubt is different than proving it beyond one.
JMO