The truth about tobacco was known for years but ignored because 1) industry lobbying and 2) the Nazis were the ones who figured it out, and pushed anti-smoking hard, so smoking became something "our side" did, 3) tobacco was still a huge US export.
It was easy to communicate, but we were motivated to not listen.
No the deaths were buried deep in the statistical data. It’s not apparent and we did not know either way.
Yes there were people who said it’s bad but their word was as good as bullshit because until we had the statistics there is literally no way to truly know.