Olives contain lots of salt so if your body is deficient in salt reserves this could easily explain why you're craving them. While it's true that on average the Western diet is too high in salty foods, it's totally possible for many different reasons that you are low on salt.

What deficiency causes olive cravings?

Olives-Craving in Iron Deficiency Anemia.

Is it OK to eat a lot of olives?

To keep your saturated fat intake within the recommended guidelines, it's best to limit your intake to 2–3 ounces (56–84 grams) — about 16–24 small- to medium-sized olives — per day. Though olives may aid weight loss, they're high in salt and fat — and eating too many of them may offset your weight loss success.