I cant find any references to Pre-Columbian Meso Americans eating anything other than unsweetened chocolate.

Is that the case?

I know they had honey, sugar, agave, etc. Plenty of sweeteners to use and they just..never added it to the bitter chocolate? seems unreal to me.

The history of chocolate begins in Mesoamerica. Fermented beverages made from chocolate date back to 350 BC.[1] The Aztecs believed that cacao seeds were the gift of Quetzalcoatl, the god of wisdom, and the seeds once had so much value that they were used as a form of currency. Originally prepared only as a drink, chocolate was served as a bitter, from a liquid, mixed with spices or corn puree. It was believed to have aphrodisiac powers and to give the drinker strength. Today, such drinks are also known as "Chilate" and are made by locals in the South of Mexico.

After its arrival to Europe in the sixteenth century, sugar was added to it, rendering it an aphrodisiac, and it became popular throughout society, first among the ruling classes and then among the common people. In the 20th century, chocolate was considered essential in the rations of United States soldiers at war.[2]