The house itself was stolen; that's not burglary?
I do wonder if it's possible to steal from a dead person without named heir(s) though....
Over here, property left by the deceased without heir is forfeit to the government and auctioned off.
If I remember correctly, USA squatters can only stake claim if the property shows obvious apparent evidence of abandonment and disuse / neglect.
Additionally, if the owners are paying property taxes, this is sufficient proof the property / dwelling has not been abandoned.
There's no such offence as breaking and entering in the uk. Burglary is breaking in with dishonest intent, eg theft, rape, assault or criminal damage. If you wandered into someone's house through an open door uninvited to admire the decor then left, I don't think you're actually guilty of anything. The difficulty would be proving your case before a magistrate or jury. if you broke a door or window in the process of getting in to admire the decor, that would be criminal damage.
I'd think wandering into dwellings, univited, locked or unlocked, much like wandering onto private property would be considered trespass. Obviously, to enter a dwelling one must traverse the property surrounding it, unless perchance one came in through the roof via parachute.
Maybe that's the difference between how things are looked upon there versus here.
Theft is permanently depriving somebody of something, which you clearly can't do to a dead person. It's not theft.
Technically, you can steal from a dead person. Though the deceased person in the OP had no clearly defined will or such establishing transferrence of ownership to another party, what would happen were a previously unknown daughter or son, sister or brother, maybe even long-lived mother or father even... what if someone came forward and claimed lawful inheritance tomorrow? Perhaps legitimate heirs weren't aware of their sibling's passing until after reading this judgment in the local paper?
Then you run up against such things as due diligence, statute of limitations, and the like. We are speaking of someone whom experienced death some 30 years ago, and birth a fair time before that when birth records were easily falsified and many even unreported.