“but halachicly if it was aser y r there gedolim that smoke”
The answer is simple. They became addicted to nicotine before they became g’dolim. G’dolim are human and not malachim. No one ever became a gadol and started smoking.
The question is why did all the yeshivas of years ago permit smoking? It was because it was out of control and could not be stopped; with a high pecentage of the hanhola and bais medrish hooked.
Unfortunately, many of these brilliant rosh yeshivas and rabbeim left wives, children, grandchilren and talmidim way too soon and suffered terribly.