When I had to clean out my mother's home after she passed I was throwing away so mcc stuff, then the estate people came (the ones that hold the estate sales you see all over) and were horrified that I threw out certain items because some people collect things we would never consider. Some folks wanted my dad's old designs he was working on for Boeing. I wouldn't let them sell it - that went to be shred. I didn't know who the real owner was (My dad or Boeing) and didn't care to find out. Bit my point is, not knowing why these items are dirty, smelly or moldy - how they came to you in the first place would be interesting to know. But I certainly would not speak ill of the party donating it, because they probably have no idea if it worth saving or not and erring on the part of caution and let someone else make the decision.
Good luck saving what you can. And don't worry about what cannot be saved.