Preheat the oven to 375°F (190°C).
Heat olive oil in a large skillet over medium heat. Add diced onion and cook until softened, about 3-4 minutes.
Add minced garlic and cook for 1 minute until fragrant.
Add ground beef to the skillet and cook, breaking it apart with a spoon, until browned and cooked through, about 6-8 minutes. Drain excess fat if necessary.
Stir in taco seasoning mix and water. Cook for 2 minutes until the seasoning is well incorporated.
Add black beans, corn, diced tomatoes with green chilies, and tomato sauce to the beef mixture. Stir to combine and cook for 5 minutes, allowing flavors to meld.
Transfer the beef mixture to a 9×13-inch baking dish and spread evenly.
Sprinkle 1 1/2 cups of shredded Mexican blend cheese evenly over the beef mixture.
Top the casserole with crushed tortilla chips and then sprinkle the remaining 1/2 cup of shredded cheese on top.
Bake uncovered in the preheated oven for 20 minutes, or until the cheese is melted and bubbly.
Remove from oven and let cool for 5 minutes.
Garnish with chopped fresh cilantro before serving.