I don't know any hoarders personally myself, so I many be off-base. But it doesn't seem that they are unable to make any decisions - they are quite able to buy

I don't know any hoarders personally myself, so I many be off-base. But it doesn't seem that they are unable to make any decisions - they are quite able to buy new items without agonizing over (say) which brand of polyurethane to buy. They can decide what to have for dinner or which pants to wear. It's specifically decisions around whether to throw away an item which they find difficult. This makes me wonder whether there is some other psychological process which makes those particular decisions hard.