To say that the Crusaders introduced the Rosary to the Catholic faith appears to be inaccurate, though. I can't imagine why anyone would be interested in making such a claim, can you?
Religious indifferentism, relativism, syncretism, a desire to denigrate all things Catholic (by implying Catholic prayer forms are not even Catholic, and originate in a religious tradition diametrically opposed to Christianity)???
I'm not sure either (although locally we have many faithful members), but I think I trust their explanation overall moreso than those writing the BMJ article.