I think that this is partially down to the language barrier. Germany’s legal system seems to be somewhat similar to the UK in the sense that the police don’t go to the CPS until they have sufficient evidence and the CPS won’t charge until they are reasonably sure that there could be a conviction. The German system probably has thresholds just like the CPS do. They aren’t at that threshold yet but they do have evidence to believe he is the person responsible. The German authorities know this is a huge case and if they strike to early and this man walks free, it would be catastrophic. I am not sure what the double jeopardy laws are like in Germany but that may be a factor too. It is wise and sensible to build the absolute strongest case possible. He isn’t going anywhere right now and I hope he is reflecting (if he is guilty) on what he has done while he’s in isolation. Nothing is worse then your own company and silence after all. They seem very confident that they have the right man so they must be allowed to build their case. If this man is guilty it is worth waiting extra to secure his conviction.