Re abandoned buildings: it’s likely due to the inheritance laws for Portugal, which are unique in the way things are automatically split upon deaths and require official signoff from all parties that are inheritors for sale. If another death occurs, then their own more inheritors for that individual.
also frozen rents: too many buildings have elders paying 50 eur rent that is frozen for decades
So landlords have no option to evict them, don't make enough money for any kind of renovations, have no option but to wait until the elders pass away and the units become available
My family is currently trying to get title to a property that should be inherited and the amount of buyouts and legal squabbles it requires just so we can repair this decrepit old building is astounding.
My guess is most families that emigrated to the US and have some inheritance right to property back in Portugal do not care to go through this legwork.