There was an effort to convince people not to vaccinate, but I think the bigger cause of anti-vaccination sentiment was contrarianism against and distrust of the effort to convince people to vaccinate. Years of government and media lies ranging from the Iraq War to distorted and propagandistic reporting of things that Trump had said resulted in millions of people justifiably feeling that the mainstream media, the government establishment, and the supposed "experts" that the media and government often trot out are all to be distrusted. It is a boy who cried wolf scenario.