or by being ostracized for drinking Cola (Coca Cola has bound it's brand tightly to the US image, which was grate for them after WW2, but is pretty bad for them now that Trump is very reliably destroying the US image).

or by most people agreeing Cola isn't healthy, so it's becomes a Luxus product they just sometimes drink and then going for a slightly more "interesting" alternative brand which fit's more the "fancy treat" vibe is pretty common (we already have been seeing this in part of Germany, where it's not rare that restaurants serve Fritz or Afro Cola over Coca Cola as the Brands "seem" more fancy while Coca Cola feels more like the cheaper non fancy choice. By being relative cheap Coca Cola might have opened created the perfect basis for it being replaced in the "fancy" context. And by it not being cheap enough it get replaced in the "people with no money" context. This leads the "in between" context (which would still be a majority in Germany) and all the US food chains etc. but only if the people don't have a personal reason to switch. Most people in Germany drink Cola only from time to time.