Depending on where you are from and what chocolate you normally eat you may find all Hershey chocolate to taste “weird.”
Hershey chocolate in comparison to European chocolate has a slightly sour or spoiled milk taste. This has to do with the recipe that Hershey uses. To make milk chocolate one can use fresh, sweetened condensed, or powdered whole milk. This will change the flavor of the final product. Hershey uses a form of sweetened condensed milk that is used by other companies to make caramels.
According to hersheys.com,
“Tanker trucks bring the fresh milk to the factory every day where it is tested, pasteurized, and then mixed with sugar. The whole milk-sugar mixture is slowly dried until it turns into a thick, taffy-like material.”
This drying process sours the milk and gives Hershey chocolate a slightly “spoiled” taste as compared to European chocolate. You need to realize that when Hershey was experimenting with producing chocolate the recipes were closely guarded secrets. He had to experiment on his own to discover a way to combine milk and the other ingredients in a way that would keep the result creamy and not curdled. Since he didn’t know how the Swiss did it he came up with another way based on his experience in adding milk to caramels, which was his first business before he went to the 1893 Columbian Exposition and became enamored of chocolate-making equipment. It took him about 10 years to come up with his recipe.
There are other specific differences between Hershey chocolate and other chocolates. For example Hershey uses cacao beans from 12 different sources to get that specific Hershey flavor. Chocolate also has to be “conched” for varying lengths of time to make it smooth, and it has to be “tempered” in order to end up with the right texture and “snap” (the way it breaks).
So if you normally eat Hershey’s chocolate and these tasted strange it could be you were eating the vegetable oil version. However, if you normally eat European chocolate then Hershey’s should taste slightly sour to you.