Coke was good, New Coke sucked, and when they went back to Coke Classic, people were so happy they didn’t even notice that they swapped out the sugar for corn syrup

While I agree with the general statement of your comment, I do wish to be a bit "um actually 🤓☝️"

The new product continued to be marketed and sold as Coke (until 1990, when it was renamed Coke II) while the original formula was named Coca-Cola Classic, and for a short time it was referred to by the public as Old Coke. Some who tasted the reintroduced formula were not convinced that the first batches really were the same formula that had supposedly been retired that spring. This was true for a few regions, because Coca-Cola Classic differed from the original formula in that all bottlers who had not already done so were using high fructose corn syrup (HFCS) instead of cane sugar to sweeten the drink, though most had by this time.[11]: 183 

The putative switch was planned all along to cover the change from sugar-sweetened Coke to much less expensive high fructose corn syrup (HFCS), a theory that was supposedly given credence by the apparently different taste of Coke Classic when it first hit the market (the U.S. sugar trade association took out a full-page ad lambasting Coke for using HFCS in all bottling of the old formula when it was reintroduced).[11] In fact, Coca-Cola began allowing bottlers to remove up to half of the product's cane sugar as early as 1980, five years before the introduction of New Coke. By the time the new formula was introduced, most bottlers in the U.S. had already sweetened Coca-Cola entirely with HFCS.[2]

New Coke was a major fuck up, but it wasn't a cover up for swapping to HFCS. Reagnomics/shifting safety laws enabled it being used, before New Coke happened.