Preheat the oven to 350°F (175°C). Grease a 9×5-inch loaf pan with butter or line it with parchment paper.
In a small bowl, combine the granulated sugar with 2 teaspoons of cinnamon. Set aside.
Add the mashed bananas, melted butter, maple syrup, eggs, and vanilla extract to a large mixing bowl. Stir until evenly combined.
Add the flour, baking soda, and salt. Gently mix just until no large streaks of dry flour remain. Avoid overmixing so your Cinnamon Crunch Banana Bread stays soft and tender.
Prepare the cinnamon crunch by combining the dark brown sugar, flour, cinnamon, and melted butter in a separate bowl. Stir until the mixture becomes crumbly.
Spoon half of the banana bread batter into the prepared loaf pan. Sprinkle the cinnamon-sugar mixture evenly over the batter, followed by about 1/4 cup of the cinnamon crunch mixture.
Carefully spoon the remaining batter over the cinnamon layer and gently spread it toward the edges.
Sprinkle the remaining brown sugar cinnamon crunch evenly over the top.
Bake for 50–60 minutes, or until the center is set and a toothpick inserted into the loaf comes out mostly clean with a few moist crumbs.
Allow the bread to cool in the pan for about 15 minutes. Transfer it to a wire rack and cool for another 15–30 minutes before slicing.