(Another) dumb question: How does dementia cause organs to fail?
Not dumb at all, the article skims over David Cassidy's years of alcohol and substance abuse which are responsible for the organ failures and most like caused or accelerated his dementia.
It is incorrect to say that dementia “causes” organ failure. Dementia is asociated with a systemic failure of the microvascular system. The vessels in other organs deteriorate similar to the vessels in the brain. Just a question of which fails first.