In a large skillet, heat the olive oil over medium heat. Add the chopped onion, bell pepper, and minced garlic, and sauté until softened, about 5 minutes.
Add the ground beef to the skillet and cook until browned, breaking it apart with a spoon, about 7 minutes. Drain excess fat if necessary.
Transfer the cooked beef and vegetable mixture to the crockpot.
Add the kidney beans, diced tomatoes (along with their juices), chili powder, ground cumin, paprika, salt, black pepper, cayenne pepper (if using), and beef broth to the crockpot.
Stir well to combine all ingredients.
Set the crockpot to low heat and cook for 8 hours, or high heat for 4 hours.
Once done, taste and adjust seasoning if necessary before serving.