Keep in mind that the British government and police did their utmost to derail the investigation.The trouble with speculation is you spend hours in your mind painting a dim picture and blame people who you don't know for something you have less hope knowing about than the cops who can't charge them for lack of evidence... not much point IMO.
I can only imagine that if Portuguese authorities had the choice between letting two murderers go or losing millions and millions of Euros because UK governments are making it difficult for their citizens to travel to Portugal for holiday, they'd choose door number one.