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I guess when you're married with kids, and you win majors...you eat better

It sounded funny when it was just inner monologue...

Duval got better after he got into such great shape. But from what I remember he kind of lost his fire for the game after winning the British Open. Something along the lines of, "Is this what the big deal is all about?"
He finally won a major and the fireworks just didn't go off for him. That happens to people in all walks of life. It's happened to me. I finally got the big house with the affordable payment, a good amount of money in the bank with which to invest, but I've come to realize that it ain't everthing. It's not the end all be all. I think that's what Duval went through. And who can blame him for it? He has more money than he'll ever need and for a time he was at the pinnacle of his chosen field. I say more power to him if he just spends the rest of his life contemplating the universe.

actually, Duval was on a rapid decline when he won the British Open. It was a fluke week for him. He was already in a tailspin. Anytime you significantly change your body type, your swing will have to change significantly as well. Johnny Miller was quoted as saying after he worked on a farm all summer, and built up some muscle, it took a long time to get the feel back for his swing.
You are right that there were other factors in Duval's decline (divorce, lawsuit from Titlelist, and Tintitus) but losing weight and working out were derfinitley part of the problem...