Set a rack in the center of the oven and heat to 375°F. Lightly grease a 9×13-inch baking dish.
Bring a large pot of well-salted water to a boil for the pasta.
Make the sauce while the water heats: In a wide saucepan over medium heat, warm the cumin and chili powder for 30 seconds to bloom the spices. Add the undrained Rotel and the condensed cream of chicken soup and simmer 3–4 minutes, stirring. Remove from heat and whisk in the sour cream and lime juice until smooth. Stir in the black beans, corn, 1 cup of the cheese, and 1/4 cup of the olives. Season with the garlic salt.
Cook the pasta 2 minutes shy of al dente according to package directions. Drain well and return it to the pot. Add the shredded chicken and toss to combine.
Pour the warm sauce over the pasta and chicken and fold gently until everything is evenly coated. Taste and adjust seasoning if needed.
Transfer the mixture to the prepared baking dish. Top with the remaining 3/4 cup cheese and the remaining 1/4 cup olives. Cover tightly with foil.
Bake for 18 minutes. Uncover and bake 7–10 minutes more, until bubbling and lightly browned at the edges. For deeper color, broil 1–2 minutes, watching closely.
Let the casserole rest 10 minutes so it sets for cleaner slices. Scatter with chopped cilantro and serve.