I don't think his strategy has failed either.
I think the goal is to find MM's body and they're giving it their best shot in an open ended investigation. Perhaps that's why it seems to be taking so long. I know HCW said he doesn't need a body to charge, so he obviously doesn't have enough evidence to charge without a body atm!
The information gathering over the past 12 months, has been, IMO partly to help form a profile of CB, other crimes committed, places homes, his geographical footprint , from 1995 - 2007 in order to possibly garner GIS data to try and locate MM. (Hence the profiling summit in Lisbon)
CB speaks German and English, so I can understand the press hits in the UK to those who may have known him, friends, ex GF's, British Tourists etc who may have interacted with him, but has there been as many press hits in Germany asking for the same info?
Hard to say. Of course, the public inquiry was based on making something public and recieve more info about CB himself and his time in Portugal. But a public inquiry has also an inconvienent side. The prosecutors are likely to get overrun by informations, that are incorrect or even false. So there is always a counterproductive part into that.
Of course, finding the body as a final prove seems the most likely legit strategy and reason, to create an almost extensive motion profile of CB.
But as long as the investigation is going on, the more and more i could imagine, that he really could be some kind of scapegoat. Of course, far away from being innocent. But putting pressure to the weakest part of a chain, will make the chain to brake very likely.
We do not know the possible confessions he may have been making in the past. Obviously CB seems to know something, but it needs holy water served as a longdrink in hell, to become coorporative. That FF statement was a clear challenge made to the prosecuters, if you ask me. So why not making public, that the prosecutors are investigating him as the perp who did it and put him into solitary confinement?
As the days, months, years go by, they all break down some day. Next step could be giving the media the info, that he will be brought into normal prison conditions, because the investigation will go on for a much longer time and they do not want to break his human rights. Does he want to sit beside other inmates, whilst everybody knows him as the "infamous maddie-killer"?
Or will he tend to save his poor life, by starting to speak about that "everything" he knows, about the poor little girl?
We'll see what happens. I still got HCW's quote from june 2020 in my mind, when he told the press that they will always have an open ear for CB 24/7, if he wants to speak about something to them.