I took it more as a way to avoid falling into the trap that "when we have more space, problems will be solved and things will be better" (in my life experience, this was a fallacy because there was an underlying issue which needed to be addressed).

Ymmv!

My mom was like that. At our vacation house she decided to have a totally unnecessary garage built. Cars were totally fine outside and as we'd meet for vacation, there'd always be two or three cars anyway so what was the point of a garage for only one car?

So she had a garage built and the day it was finished, she started buying shelves, shitloads of shelves and then a... Ping-pong (aka tennis) table.

You couldn't even park a car anymore in the garage: an argument even ensued for I was outraged that after all that talk about a car garage, it wasn't even possible to park a freaking car in it.

Most of it was useless junk that I ended up recycling.

I can understand when it's related to a hobby: whatever the hobby, once you begin, it's like Pokemon... You want to catch them all.

But just buying random items for the sake of hoarding? Like fake, pluggable, electric candles: she'd buy 3 times the same and two would be stored should the other fail. Or that knife that'd take a battery and play a crappy lo-fi version of "happy birthday" when cutting a cake: darn did that thing traumatize me (for she bought it when I was already an adult).

There are actual compulsive hoarders (like my mom) but also those who do hoard but where it's less obvious: the Diderot effect you're talking about.

Buying empty space to then fill it. Arguably with more emptyness.