zvei dinim -“My question now is: how can we turn the above stated fact, that smoking is assur, into the strong mainstream opinion?”
This is an easy answer. The Yeshivos would throw out smokers & not allow it. I know of one Yeshiva that doesn’t allow it & it’s not just lip movement.
Why it’s not part of their rules, esp. since they have so many constricting rules, is a question that you have to ask the people running these Yeshivos!