Having one Croatian in every team that have won the champions league from 2013 is just a coincidence.
Of course it is just a coincidence and it doesn't mean that team has to have Croatian player in order to win Champions League but it is interesting anyway. If anything, it says that Croatian players play in the top world team, therefore they often win CL.
I can't believe that people thought that there is actually something behind it and that I have to further explain this football joke that goes around for years...
Coincidence remains just a coincidence. So we can't take it seriously. But the many coincidences in a football match or in the outcome of a competition is what makes all of this even more interesting. We don't need to be too serious but we can enjoy it or even speculate in that direction.
I personally prefer to speculate on the ability of a team. But sometimes there are many surprising match results. So that even an advantage in game performance cannot even be a benchmark for getting victory in a soccer match. because it is the ability in the field and a mature strategy that we can usually hold more to make a team superior.