Coke is downstream of Sugar and Artificial sweetener manufacturers. Coke doesn't care what sweetener you prefer in their products as long as they make a profit.

Aspertame was owned by Nutrasweet, where as big sugar, is, well, sugar cane and sugar beet plantation owners and processors.

Both of them were competing with each other for adoption in products and when sold direct to consumer (I.e, equal). They both had a vested interest in slandering the other.

See this as an example.