Society has changed its view on smoking since the 1960s. what was the major cause of this change

The major cause of this change is that scientists showed that smoking leads to cancer.

Explanation:

After performing some monotonous experiments and tests in the later parts of the twentieth century, scientists have demonstrated certain proof that the substances and chemicals present within a cigarette can lead to diseases in the long-term like cancer. In the 1940s and later years, the cases of lung cancer and lung diseases got increased, however, it was considered to be a very rare disease. However, with the help of certain experiments, society's view of smoking got changed after 1960 as smoking can lead to cancer.

not sure if this is what you'r looking for eubacteria and archaebacteria