Asked if they would buy and drink the product if it were Coca-Cola, most testers said they would, although said it would take some getting used to. About 10–12 percent of testers felt angry and alienated at the thought, and said they might stop drinking Coke. Their presence in focus groups tended to negatively skew results as they exerted indirect peer pressure on other participants.[9]: 355

So face-to-face focus group marketing studies said this 10-12 percent of people is skewing the results by exerting peer pressure.

Guess what happened when they released it.

Bill Cosby ended his long-time advertising for Coca-Cola, claiming that his commercials praising the superiority of the new formula had hurt his credibility.

Even Fidel Castro, a longtime Coca-Cola drinker, contributed to the backlash, calling New Coke a sign of American capitalist decadence.  Goizueta’s father expressed similar misgivings to his son, who later recalled that it was the only time his father had agreed with Castro, whose regime he had fled Cuba to avoid.

Conspiracy theories:

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). 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

https://invidious.privacyredirect.com/watch?v=4rnwwH6Lum4

or

https://youtu.be/4rnwwH6Lum4

The press conference at New York City’s Lincoln Center to introduce the new formula did not go well. Reporters had already been fed questions by Pepsi