Jees, I am not a researcher but it seems it has a lot to do with luck. Perhaps it is as simple as breathing in a toxin on a bad day, when the immunity is a little low and for whatever reason a cell goes a little awry...and the foundation begins.
It may be that simple, but as long as there is something easy to blame, will we ever know?
I would rather see the resources spent on understanding the fundamentals of the disease and finding a way to short circuit it, so to speak, than whining about cigarettes. If we can cure it, the cause becomes moot.