

Aspartame’s patents expired between the late 80’s and early 90’s. Current limits were set after that and have been reviewed as recently as 2024. I’m going to say that the ability to patent and monopolize aren’t really a factor since aspartame hasn’t been protected in over 30 years and a search to see who produces it returned an article listing the top 100 manufacturers of aspartame.
Did a quick search, in higher doses stevia may cause mutagenic effects and regulatory bodies initially classified it as safe over the objections of some researchers who say it needs more studies on this effect. Stevia also lowers blood pressure and can cause light headedness and fainting in larger doses. The effect on blood pressure is potentially fatal in small children and people with certain health complications.
In less refined forms stevia also carries a high risk of allergic reactions because it’s a form of ragweed but the stuff used as a dietary sweetener is highly refined so that shouldn’t effect the recommended limit.