He ran a horrible campaign and his heart just wasn't in it. Somebody on TV was discussing the '92 election and kept mentioning 41's health problem. I can't remember what that problem was?
Lack of a spine.
Instead of standing up for Republican principles, he caved on too many issues, including "no new taxes" and the gun import ban.
By 92 I was sick of him, which is why I voted for Clinton, who at least appeared (although it soon became obvious it was just dishonest PR) to have actual principles and ideals and pretended to be more middle-of-the-road than Bush 41 turned out to be. At the time Clinton seemed less liberal than Bush 41.
Okay, fine, I was an idiot, and quickly learned the error of my ways, the fact remains that Bush 41 sold out his alleged principles and alienated his base, just as the book excerpt which starts this thread points out.
Graves disease.
I quote from the National Graves' Disease Foundation Website:
"The leading cause of hyperthyroidism, Graves' disease represents a basic defect in the immune system, causing production of immunoglobulins (antibodies) which stimulate and attack the thyroid gland, causing growth of the gland and overproduction of thyroid hormone."
Both George H.W. and Barbara Bush were afflicted with it.