@BogRollBOGOF I read your overall excellent post nodding away, especially regarding how health can suddenly go, and that most squalor hoards didn't start out that way, and it is when control is lost and all descends to total chaos.
But while you might be correct about your mother, you know her and clearly have lots of insight into her, and I'm sorry for your struggles with her, I'd suggest people should be cautious of generally seeing hoarding as just an "irrational addiction to possessions" even though it feels like it might fit many.
I don't think I'm eloquent enough to fully explain why, but there's a danger of falling into simple narratives that then gain traction and send people in the wrong direction both in seeking, and in offering help.
The 'selfish/mean, mad, bad miser' trope helped isolate and shame under the idea that HD was a personality defect and personal failing. (many of us carry huge shame and failure)
The 'almost impossible to treat' claim, grew up because of wrong understandings and wrong treatments, starting with classifying it as a part of OCD and then seeing those with HD as hard to reach when OCD treatments didn't work on them, rather than the premise and treatments where wrong.
Motivational Enhancement Therapy and Twelve Step Facilitation became a thing for quite a time, when HD was seen as another kind of addiction, but did little for most, further embedding the idea that it was treatment resistant, rather than these where the wrong treatments.
Then EDMR suddenly appeared as the simple miracle treatment to 'process trauma' therefore would 'fix' hoarding disorder as much is trauma based, and lots of desperate people lost huge amounts of time, money and hope.
Having an "irrational addiction to possessions" does sound a lot better and more socially acceptable than "lurching through life deeply damaged and suffering extreme maladaptive responses" but labeling it as the former may not provide much needed answers, or even questions.
Most especially for those with complex hoarding disorder, and where disassociation and depersonalization are involved.
Also those unable to hold memories without three dimensional haptic aids (part of why photos don't always work for some) and anything that is not in front of them (including in cupboards etc) ceases to exist along with all memories around it.
As well as those individuals whose extreme socially maladaptive hoarding behaviors include being unable to dispose of bodily fluids, nail clippings, hair etc
Whats going on with some with HD isn't easily correctly explained...