That on’s probably also because Smokefree Aotearoa was introduced under John Key’s National Government in the first place.
Tariana Turia spearheaded it when the Māori Party was in coalition with National, it came out of a Māori Affairs Select Committee process back in 2011 but John Key was totally on board with it and every iteration of the goverment has been.
It’s not a National vs Labour issue and no one had any reason to think it was about to be derailed. We’ve collectively spent a fortune on it, and no one is particularly passionate about making young people start smoking (except tobacco companies).