I have already explained countless times the most rational explanation is that already put forward by the Police, the one backed up by the evidence and the circumstances.
You've got a very strange concept of evidence.
If there had been any substantial evidence that would have stood up in a court of law, either in Portugal or the UK, then I'm sure that the McCanns would have been charged by now. They haven't because there isn't.
I haven't seen the Netflix documentary but I wouldn't be surprised if they criticised the initial response by the Portuguese police who failed to secure the crime scene promptly thus jeopardising their chances of finding forensic evidence. They may have even mentioned that when fingerprints were eventually taken the forensic officer fucked it up and compromised the crime scene by leaving one of his own prints.
The Portuguese investigation was an absolute shambles from the outset, culminating in the convicted perjurer Amaral being removed from the case for leaking details of the investigation to the press.