Hoarding IME has been about severe resource anxiety -- not unlike the fad of prepper and adjacent lifestyles, but rather generalized in contrast. It's an attachment to, even a personal identification with, the hoard of goods that the afflicted have collected and stored.

Anecdotally, it seems to have affected a high proportion of the Silent Generation -- those who grew up in scarcity (Great Depression, etc.) but then experienced in their adulthood the social pressures toward consumerist abundance. Being afraid of suffering what is seen in retrospect in such societies as an undignified and painful life, they seek to collect things (value, utility) that will ensure they never again experience the same feelings of destitution.

So it makes sense in the current climate of economic precarity ("one bad accident away from total ruin") that such feelings are surging again.