Not sure if this is the right place for this, but how come in pretty much all cultures, dragons showed up a lot even when said cultures had no way of communication? eg. in china, japan, ancient Egypt, etc.

Bad translations that shoehorn entirely different things under the same label. More can always be said on the matter, so if anyone would like to address the (mis)application of the term 'dragon', please feel free to do so! For the meantime, OP, here's u/itsallfolklore addressing the ostensible commonality of the dragon.