My pet theory is that New Coke was always meant to be a temporary and not a permanent Coca-Cola brand product. Because when Coke Classic was “brought back” to shelves, it was made with corn syrup and not cane sugar.
I think New Coke was meant to “cleanse the palletes” of consumers to what Coke made with cane sugar tasted like. When folks had voiced enough displeasure with New Coke and the coming “Classic” corn syrup formula was ready to roll out, New Coke was withdrawn.
I think consumers in the main were overjoyed to see “Classic” “return” and never noticed any real difference between what was before and what came after. (Thanks in part to the taste of New Coke, which was very different.) Some still noticed the difference, preferred the earlier product, and now buy glass-bottled Coke made with cane sugar from Mexico.
...But history undercuts my theory: Coca-cola was already being made with corn syrup before New Coke was rolled out. The switch was earlier.