The reason for the incredible variety of dragons in different cultures is most likely just a case of misleading translation. The Chinese dragon and European dragons don't have much in common for example the European dragon is associated with fire while the Chinese dragon is most often a wind or water elemental. Dragons are also not always harmful in Chinese culture they can be a sign of luck or good fortune often times. The thing is that all kinds of beast are translated to dragon in English there is a legend form Moldova for example that is called "basil the handsome" in that myth there are 3 creatures called dragons who all have different features of donkeys for example and have nothing much in common with the fire breathing flying lizard that we associate with the term dragon.