Our first house was like that - smaller but similar condition. It took two lorries to clear out the junk (and this was after the sellers had moved their stuff!) but I'm glad we did it because we salvaged a few useful things too. It looked so bad that other buyers had overlooked it and it got us on the housing ladder. I'm all for property presentation but I don't have much sympathy for people who can't see past a house's condition.
I agree there probably is a sad story but it may well be a person who people have been trying to help - MNers have posted before about parents who are life of grime style hoarders and how frustrating it is.