I totally relate to what you're going through right now. We went through a modified version of that when my FIL died. He kept almost everything, but the only place that it really was a horder's haven was in his single car garage.

FIL's estate paid for one of those gigantic construction dumpsters...the kind that arrives on the flat bed of a semi. We filled it up in about 3 days.

At first, DH & SIL insisted that we sort through every scrap of everything. UIL chimed in, too. I was so mad that they were spending all of that time, energy, and effort on stuff that was worth nothing. For example, FIL had a ton of scrap wood and screws, nuts, and bolts in his garage. None of it was organized in containers or anything. Just piles of screws, nuts, and bolts and stuff.

FIL, DH, & SIL all discussed it and insisted that all of the metal stuff be set aside to be taken to a recycling center for money because "it's worth something!" 24 hours later, after spending 12+ hours per day sorting through crap, and all 3 of them decided together, "You know what? Forget it. This is taking forever and we'll spend more money on gas getting to the scrap metal place than we'll get from this."

And then it all went in the trash bin.

After that, the throwing of stuff into the trash bin went much faster. They all had to reach that point on their own. BIL & I, being the spouses, just sat back and did what we were willing to do, but we didn't try to influence any of their decision making.

Trust me....let them sort through MIL's disgusting trash. You should stay away and not expose yourself to stuff like Hanta virus and other crap from the rodent droppings. You can support them by bringing them snacks and water to drink. But stay away other than that. Give it a few more days and they will reach a point where they can't take it anymore and they will just chuck it all in the trash like they should have from the beginning of all this.