People bring their own bias into a story like this and I'm no different. My take on it is that the Portuguese police were getting slated by the British media for their incompetence investigating the crime - the normal idea is that the family should be the first to be suspected and investigated, not leave it a fortnight or so before looking into that. Also, the local tourist trade was being hit. Thirdly, it later became known that the local police had turned a blind eye to breaking and entering and petty theft all along that resort, possibly because they were mates with the local criminals, it seems likely.
With all that in mind, and with shadow being thrown at the police and the press badly needing a new angle, the police did the usual conventional thing, the only thing possible in those circumstances - they victim blamed. They started to put it about that the parents had a part in the murder. We saw it with Hillsborough, the Contaminated Blood scandal, the Post Office scandal and so on, possibly Lucy Letby, it's basic police procedure.
And people feel less sorry or heartbroken over the situation then because they feel the parents were responsible and at least knew what occurred.
After that the Met got a few freebies in sunny climes 'investigating' the disappearance and bizarrely managed to turn up not one instance of any paedophile ring or such behaviour in the course of their inquiries over many years. The German police seem to have sorted this one, however.