Some people do become hoarders because it is too difficult physically to get stuff into the trash cans. Some people get depressed and can't throw things away. Some people lose motivation because no one is there to help with the job. A stroke might have changed his personality. Or the hoarding might have gone on a much longer time without anyone knowing about it. Hoarding also often quiets anxieties about life and living, kind of like cutting oneself.

I'm sorry for your loss. Too many people get disconnected from friends and family, who can help, in this modern world. Sometimes I think the only solution to the problems single people often face is a return to living in small bands.