1.Preheat oven to 350°F. Place graham crackers in a food processor until they become crumbs.
2.Mix the graham cracker crumbs, melted butter, cinnamon, and sugar together in a medium bowl until combined. Press the mixture into the bottom and slightly up the sides of a 9-inch pie dish. Make sure it is tight and compact.
3.Bake the crust for 16 minutes. Remove from the oven and allow to cool for at least 30 minutes before adding the layers.
4.Meanwhile, using a stand mixer fitted with a whisk attachment, whip the heavy cream, powdered sugar, and vanilla on medium-high speed until medium peaks form, about 3-4 minutes.
5.Spread dulce de leche on top of the crust. Arrange banana slices in 1-2 layers on top of the dulce de leche, then spread whipped cream on top.
6.Refrigerate pie uncovered for at least 2 hours and up to 1 day. Garnish with toppings before serving, if desired. Cover and store leftover pie in the refrigerator for up to 5 days.