Maybe he was that good. Maybe he was just lucky. Maybe the original investigation was inadequate. Maybe it's a combination of the three.
He got away with the DM rape for 14 years, a crime where he was shown to be quite savvy and cautious not to leave any trace. He would have continued to evade justice for that if it wasn't for a single rogue hair.
Suggesting that some kind of fit-up must be going on due to the fact that SY didn't catch him earlier is completely illogical though. It was the Germans who discovered CB's number, had SY known about his number when they were investigating those three other local burglars, I've no doubt CB would have been a major focus of their enquiries too. If not the main focus, since in addition to his burgling activities, he also had a record for child sexual abuse.