For instance, they disrupt your metabolism, so equivalently sweet amounts of sweeteners cause more weight gain than sugar. (Due to increased hunger vs. eating nothing, decreased metabolism and decreased calorie burn.)
The study in the article isn’t surprising at all. Links between nutrisweet and migraine headaches have been well understood for a long time. It’s not surprising other similar chemicals have similar negative side effects.
There’s no valid reason to use artificial sweeteners (other than diabetes, but even then, gaining weight from the sweeteners is a problem if the diabetes is weight related.)