Correct me if I am wrong, but I don't think the german police have released his name, it was the media here who announced it.
Police clearly did not try to keep CB's identity a secret. They banked on the media outing him and painting him as a 'serial killer'.
In my view the police have lots of circumstantial evidence (phone logs showing presence near crime scenes, several acquaintances who heard stuff from him that seems to link him to MM's abduction...) and a psychological profile (not least courtesy chat logs) that depicts this man, a convicted paedophile and violent rapist, as someone who is sadistic and fine with killing the child afterwards.
But they have no proof. So they out him, 'allowing' the press to put the jigsaw puzzle together, branding him a serial killer. This way they can dissuade courts from releasing him early, dissuade courts from showing lenience or appyling 'in dubio pro reo'. They know they probably won't ever be able to convict him for MM and the other kids, so they basically try to keep him in prison for everything else.
This is very troubling from a 'rule of law' perspective (even though I understand the motivation, considering they are probably fully convinced he did it).