You cut out the part that said the diets improved people’s health at 6 mo. But they were hard to maintain for 12 months. I think a lack of consistency is the issue. From your link:

>What if they'd lasted 12 months, or two years, or a lifetime? The benefit would likely have been greater and more long-lasting. The trick is to pick a diet with foods you actually like so that it's not so hard to stick with it.

Meaningful behavioral change is hard, especially in a modern food environment.