You missed the best part, they have always known that NutraSweet and aspartame are toxic, they knew before it was allowed on the market, so how could a known carcinogen become an approved food additive, for the real answer you would have to ask none other than Donald Rumsfeld.
yeah, this Donald Rumsfeld:

https://dailyhealthpost.com/the-shocking-story-of-how-aspartame-became-legal/