Here is a theory. Perhaps you picked up some second hand cig smoke in one of your articles of clothing while in Europe. Maybe you didn't notice it at the time because it's cold there and you were sniffling. Sweaters and thick natural-fiber fabrics hold in smells much more than thinner fabrics and oil-based fabrics. Once that item is in your bag the smell permeates throughout the bag and "infects" the other items.

I did not know about the special smoking rooms for employees at CDG and AMS. However I would think these would be for breaks and not the actual rooms where they are doing their jobs.

Over the last few years I have found items in my bags (when opening at home) that do not belong to me: 1 sneaker, a hand towel, a t-shirt, socks, etc. Are you sure you don't have an article in your bag now that was not there when you packed up in Europe? Again, just grasping for an explanation as I find it so very strange that your clothes could end up smoke-filled from (what I imagine to be) normal airport luggage screening procedures.