The inclusion of Monk in D&D/Pathfinder is kind of fascinating because even Paladins have a sort of vague precedent in fantasy fiction but their whole thing is "have you ever seen Kung Fu with David Carradine?"
Druids are so oddly specific. Cleric, Rouge, Paladin, all very general templates. Then there's "I want to play a shapeshifter" and then it became a whole core class. Such a wild ass niche mechanic to build a whole class around
While it is certainly true that traditional western fantasy fiction doesn't have Kung Fu monks (as far as I know), Eastern fantasy fiction often does. Having them both exist in the same world makes sense to me due to most game worlds being massive realms with many different cultures.