Remember he was a burglar as well as a paedophile. He may have been looking for valuables, passports, anything he could flog to sustain his lifestyle, and came across the children by chance. The geography of the apartment meant it was the easiest of all the Tapas 7 accommodation to break into.
The McCanns did not claim anything had been taken or moved in the sense of looking for valuables.
Think statistics. What would be the statistical chance of a burglar, come paedophile, happening upon an unlocked holiday apartment with children under the age of 4 unsupervised?
According to Wiki PDL is home to a permanent population of 3,500. Obviously this increases in line with the tourist season. 3.5k gives some idea of the number of homes. As far as we know no one reported a break-in or attempted break-in that night so again I come back to statistics: what are the chances of a burglar, come paedophile, happening upon an unlocked holiday apartment out of all the possibilities of other properties in PDL with children unsupervised?
Its not plausible and statistically highly improbable. I come back to the biggest clue: the person(s) who abducted MM knew she was unsupervised in the unlocked apartment. This narrows it down to a handful of people.