Because there’s a general move away from US products in the EU due to the souring of US-EU relationship since Trump became president.
Coca-Cola is one of the brands that is extremely well known for being from the US. As such it would be easy for people to boycott, even if they didn’t do their research regarding which brands are from the US originally.
lol. Not sure where you think you saw an ad campaign. If anything I saw the public spontaneously boycotting way faster than the average government based ad campaign could have been arranged. If there has been any campaigns (and again: I am aware of none) then it was after the public already started boycotting by themselves. Source: I live in the EU and saw this happen and had conversations with people around me about the boycotts too.