This isnt really true. Its small preliminary research that just suggests an area of further research. It certainly doesnt prove anything.
A group of smokers had more hair loss than non-smokers. It could be from many many things besides the smoking. They have no way of figuring this out.
There are some super smart genius scientists out there though that could understand and figure out almost anything of any complexity. Its just we lack so many pieces, and its so hard to figure out what does what. That is why we can only guess at this. What we know moves so slowly.