I'd argue the drastic reduction of smoking is the result of a culture shift around the activity (better education) and governments banning it from public spaces, not lawyers suing Philip Morris.
I think it's pretty hard to say that that cultural shift happened in isolation from the reduction in commercial advertising of tobacco products (due to legal bans in the 70s and 80s) and the associated increase in advertising of their negative effects (often paid for by lawsuit settlement money).
Those companies spent billions to shape the cultural perception of smoking through direct advertisement and popular media.
Yeah, given shifts in social consensus also provide lubricants for lawsuits (and laws). One would have to study the issue harder than I have--and I'm sure people have and probably written books. But certainly there was a massive shift in most places that probably isn't explained by either legal actions or higher taxes.
