"And all that time, he kept from them, his knowledge that she did not want to live that way; he kept that denial of her wish, for nearly 8 years."
Did the possibility ever dawn on you that in those first years they were busy trying to save Terri, flying her out to California for rehabilitation, and the topic never came up? Why would it. At that time they thought they still had some hope for Terri's rehabilitation. As the years passed, it became much more obvious that that wasn't going to happen. When Michael got to the point where he was convinced by doctors that nothing was ever going to improve for Terri, and after he and the parents had their falling out and had competing ideas about what to do about Terri, that's when the subject had to be discussed seriously. The parents wanted one thing; Michael knew what his wife had said in casual conversation (heard also by 2 others besides himself) and he wanted to honor Terri's wishes which were different than the parents. Under FL law, the spouse makes the decision, and Michael did. You don't give up hope on a loved one right away. It's as time passes that you become more and more reconciled that there will be no improvement, ever. So, use some logic here about how things really play out in life, rather than the story you'd prefer to concoct in order to slam Michael. By the way, all this stuff is in the court transcripts. Go read up.
He denied her wish, and he did so, for nearly 8 years.
During all of which time, he failed to reveal in probate, her wish, and then petition in probate, for opportunity to see if things improve.
Changes to wishes and wills of incapacitated people, are made in probate; especially life and death cases.
"Just in case" would be why.
Quite clearly the fact that they resorted to experimental treatment shows that they had little hope in conventional medicine at the time; any sane person would be thinking about the "just in case" scenario.