Feeling really sad

My partner and I moved back to his parents farm with the plan to take over the farm tenancy. His parents have moved out but left the farmhouse hoarded. He has, after much pushing, admitted he is too scared to ask his mother to move her stuff out or give her a deadline (we know they don’t work but at least it would demonstrate to me that he is prioritising our takeover) or to contact external support, or even to have a conversation with her about her hoarding. I don’t know where to go from here. The whole of the last four years we have been working toward the takeover, have worked our fingers to the bone clearing the place up and getting animals in better shape, to then at the final hurdle essentially say that his mothers hoard is more important than us taking on the house too. Oh, but we are paying rent for the house to be a storage museum of her stuff. AITA here? I am a bit blindsided by his 180, but should I be more compassionate toward him as he clearly has a LOT of trauma around their last move when he was in his early 20s and had to manage his mother then, who was by all accounts, a nightmare. She will has a skip full of rubbish from that last move that has sat in the rain for 20 years. Do I try and be compassionate , or am I justified in being pissed off that the rules have changed and we are now to live our lives around her mental illness? The mother is a sweet lady all in all, an information hoarder, but I have been on the receiving end of her tongue when I have thrown stuff away before. My partner, in his 50s, is clearly terrified. I was def talking to his inner 7 year old…..

Help.