The detectives were only doing their job since the evidence indicated that there might be more to the disappearance than first realised. What always surprised me though was that they were even allowed to leave the country under the circumstances.
Could it be that they were shocked by the reaction of the crowd on the day of the arguido interviews in Portimao?? Far from making friends their were deemed to be pariahs.
Why would they be shocked? They had seen themselves made victims of a poisonous smear campaign in the press, aided and abetted by certain PJ officers. Do you think they didn't know how that would affect the opinion of a proportion of the Portuguese population? But not everyone in Portugal held those opinions - and they did make some good friends over there.
As for the police 'only doing their job' - I'm afraid that is not an opinion I can share with you. It is plain that some officers were honest decent policeman who did their level best, but unfortunately not all. IMO There were corrupt officers who just wanted a result - any result. Innocence or guilt didn't really come into it as their subsequent criminal convictions for grossly abusing their power as police officers by the use of perjury and torture to 'get a result' was to prove.