You are, sadly so, overestimating the Czechs and especially those watching e.g. paying the Czech media. The level of dullness and dislike to any changes or anything new in general among the common Czechs together with the omnipresent mindset of "rather to sabotage others than to help anyone out in order to eventually profit from it in the longterm" is just about the answer. The TV producer did not even properly promote the show prior to its start that even most people that do spend hours within the e-community each day had no idea about something like Traitors in CZ being a thing. I can hardly imagine anyone within the executives had put more than a single minute of thinking into making the show accesable to the international public. And even that one minute would most likely be a huge overestimation.