There is something which I think there is some confusion about here. Saying that something is assur can mean different things. Even if the Gedolim assurred smoking, that does not put it in the category as something that is mamash assur such as being mechalel Shabbos.
Also, some posters had mentioned that at a certain point, the Gedolim did not yet know that smoking was dangerous. I had also always been under that impression, but I actually saw in one of the Chofetz Chaim’s sefarim that he wrote that smoking is assur. He gives two reasons: 1. it’s unhealthy 2. waste of time (in those days it took at least half an hour to roll up the Cigars).