Why would a cat stop eating? (triggers)

[hdme]

My dad had moved into a new apartment in May and had given his 10 yr old cat to my brother and his wife since he did not want to bring the cat into a brand new apt and no longer wanted to leave the cat alone while golfing and running errands all day, everyday...he wanted the cat to have more companionship. My brother has another cat and a dog.

On the day my brother took the cat, he immediately brought him to a vet who put the cat on diet food. They saw that the cat was eating sometimes, but after a couple of weeks, my SIL noticed the cat was not around much and when she did see him, he looked thinner. They brought him to the vet where he stayed for 2 weeks having tests run on him. The vet said something was wrong with his liver because he was living off of his body fat instead of his food. The cat died last weekend in the middle of the night at the vet's office. When I ask my dad what he died of, all he says is liver failure.

No one can tell me why he stopped eating though. Could it have been his age and weight finally got to be too much for his body to handle? Could his liver have been giving out before my dad gave him to my brother and that's why he stopped eating? Needless to say, dad is very upset and feels like it was his fault for giving the cat away...I'm trying to reassure him that it could have happened regardless of where the cat was living.