Calories isn't everything, there is a lot more focus these days on how different foods affect metabolic hormones affecting satiety, blood sugar, etc. On those metrics, fat alone (which account for most of the calories in peanuts) is very satiating and does not trigger a later blood sugar drop (which causes cravings). That's why people on a diet drink 'bulletproof coffee' (coffee with butter in it), because it is extremely filling while not making you hungry later.