It is not likely Croatia would have done this. They are pursuing Nato membership. It is more likely some other nation sold this system to Iran and wants to divert the attention of the West.
During the Balkan wars Croatia was the most corrupt country in the Peninsula. It allowed its territory to be used to supply the mujahideen, and Croatian officals from top to bottom were on the take. If you go back to the post-Tito period you will find that the fascist (and it goes without saying, anti-Semitic) Croats who had found a home in southern South America made a beeline for home. Many were soon placed in high government positions. It is my hope that NATO has nothing to do with Croatia.