I'm sure some have picked the hoard over their partner
The majority of "not a mild case" hoarders pick the hoard over everybody. Including themselves. Their health, wealth, happiness, and their entire life handed over to the required service of The Hoard.
One of the saddest stories I watched unfold in a support group was when a hoarder died. Her son, not a hoarder, had to travel several states away to deal with her house. Leaving his fiancé back home while he got it done. Her last post, two whole years after he had left for a six week trip, was heartbreaking.
"He's still churning"
His mother's legacy to her (formerly non hoarding) son was such a degree of guilt created over throwing away what meant everything to her that despite running from the hoard a decade earlier...he clicked into her habit. Of moving mounds around, shifting through piles, but never actually getting anything out of the house. She died, and "nature/nurture" sucked him into her place. I doubt she would have chosen that for her only child if she'd had a wholly free choice. But the compulsion made the choice for her. And they both ended up drowning in the result.
Hoarders, despite all the divorce threats they make if the hoard needs protecting, don't tend to leave people, even if you do a blitz while they are out and they come back to what to them looks like the biggest betrayal ever known to mankind. You'll pay, but not in the way they promised you would. They generally can't leave, or instigate separation. Cos home is usually where the hoard is. Splitting up the family often puts the family home at risk of sale, which means the hoard is at risk of being touched by somebody else to shift it all out. And then having nowhere big enough to put it.
The majority of them, once a certain point is reached, can't find a way back to a state of controlling the urge to hoard, regardless of threatened consequences. Not even when the threats are the removal of the children made by social services. It becomes a game of one step forward. Then two back as soon as the urge gets too strong to fight. Dire threats are carried out. And still protection of the hoard carries on.
Partners, family members, children of hoarders tend to be the ones who instigate separation. Because they reach a point where they recognise that the only person they can save is themselves. They could spend a lifetime with a hand held out trying to haul the hoarder out of the clutches of the Stuff Tsumani and the result would be the same as if they had thrown the towel in and walked away years ago.
There is nothing wrong with trying. Just because there is a high fall back rate and a high family break down rate doesn't mean in any individual case there is no hope and no point in trying to see if the person you love is the one that can buck the trend with the right sort of help.
However, everybody should have an exit plan.
Spouses are better off if they have already established with a legal professional where they stand custody/division of assists/maintence wise, well before that information starts to look like it might be needed in practice rather than theory. Because you can't build a reliable exit plan on assumptions based what held true for somebody else when they divorced.
Dependants are better off if they start salting away a "just in case I ever need it" savings plan. So the actual means to leave are there, if a crunch point arrives. Sudden, dramatic hoard downward spirals do happen. They can be linked to a stressful event, or just that a tipping point was reached and all semblance of control was let go. These sorts of sudden, dramatic hoard spirals can leave the other occupants left high and dry if the house becomes infested, dangerous, damaged (but unfixable due to lack of access and shame) and they have to start creating their economic exit plan from scratch, at one of the lowest points of their life.
It's OK and perfectly normal to hope for the best, but having to plan for the worst is unfortunately part of the reality. Because the compulsion that created the hoard tends to win, and the people tend to lose.