The lifestyle changes he made were probably too little too late. He probably already had cardiovascular disease.
Allen Carr, the author of easy way to stop smoking - he died of lung cancer, because the damage had already been done. But what he did has and still does help many people. Comparing this to what you said in the original post; does that mean smoking doesn't cause lung cancer?
Eating healthily can only be beneficial to a persons life, but it doesn't mean that you're going to live forever. Nobody ever claimed that.