Preheat oven to 325°F. Wrap the outside of a 9-inch springform pan with a double layer of heavy-duty foil to prevent butter leaks.
Make the crust: Mix 1.5 cups graham cracker crumbs, 2 tablespoons granulated sugar, and 5 tablespoons melted butter until it resembles wet sand. Press firmly into the bottom and halfway up the sides of the prepared pan. Use the bottom of a measuring glass to flatten. Bake for 10 minutes, then cool on a rack.
Make the blueberry compote: In a small saucepan, combine 2 cups blueberries, 1/3 cup granulated sugar, and 1 tablespoon lemon juice. Simmer over medium heat for 5 minutes, mashing a few berries. Stir together 1 tablespoon cornstarch and 2 tablespoons cold water, then pour into the berries. Cook 1 minute until thick. Remove from heat and cool completely.
Make the cheesecake filling: Beat 24 oz room-temperature cream cheese and 1 cup granulated sugar in a stand mixer on medium speed until smooth (about 3 minutes). Scrape bowl. Add 3 large eggs one at a time, beating on low just until combined. Mix in 1 cup sour cream, 1 teaspoon vanilla extract, and zest of one lemon until smooth. Do not overmix.
Assemble: Pour filling into cooled crust. Drop cooled compote in 8-10 small dollops over surface. Use a butter knife to drag through in a figure-eight motion—two to three passes only. Over-swirling creates a muddy mess.
First bake: Place springform on a rimmed baking sheet. Bake at 325°F for 30 minutes. Cheesecake should be set at edges but slightly jiggly in center.
Make crumble while cheesecake bakes: Combine 1/2 cup flour, 1/2 cup rolled oats, 1/3 cup packed brown sugar, and a pinch of salt. Cut in 1/4 cup cold butter until clumps form (pea to marble size). Chill in freezer for 10 minutes.
Add crumble and second bake: After the first 30 minutes, remove cheesecake from oven. Sprinkle crumble evenly over top. Return to oven and bake 25-30 more minutes until edges are set and center has a gentle wobble. If crumble browns too fast, tent with foil.
Cool slowly: Turn oven off, crack door open, and let cheesecake cool inside the warm oven for 1 hour. This prevents cracking.
Chill overnight: Remove cheesecake from oven, run a thin knife around the edge, and cool completely on a wire rack. Cover and refrigerate for at least 6 hours, ideally overnight. The texture sets and flavors meld during this rest.