As BCB outlined above, hard to blame the Gardai when what seems to be a reliable eye witness picked him out as the assailant, there was proof he was in the area and he was known to police. It looked like it had to be him and they just had to piece it together. The house was ransacked during the investigation, not after they had all the evidence that cleared him.
It seems awful what happened to the Romanian family. The sister must have had some reaction to get herself arrested. According to the original suspect, she has mental health problems, so all very unfortunate and presumably they are entitled to compensation.
At least they seem pretty sure they have the right guy now. Not sure how BCB knows what he looks like, but he says he looks very similar to the original suspect