Diplomacy is quite a bit different because you 100% win by being the nicest asshole. Past a small mechanical threshold, there really is no way to make it up in strategy or luck, it is only the interpersonal relationships and convincing that wins games. That, coupled with the fact that the game takes a long time and encourages a lot of communication, means the recipe to get invested and blur the boundary between game actions and lies people told you to your face and got you to trust them, can be very unlike risk. Finding out your friends can lie and manipulate you can be like finding out Santa clause isn't real.