Stir graham cracker crumbs, melted butter, and sugar until it looks like wet sand. Press firmly into the bottom of a 9-inch springform pan using the bottom of a measuring cup. Chill while you make the filling.

Beat cream cheese on medium speed until completely smooth, about 2 minutes. Add powdered sugar and beat until fluffy and no lumps remain, scraping down the bowl twice.

In a separate bowl, whip cold heavy cream to stiff peaks, about 3-4 minutes. Fold whipped cream and vanilla into the cream cheese mixture in two additions, cutting through the center and turning the bowl until just combined and no streaks remain.

Spread filling evenly over the chilled crust, smoothing the top with an offset spatula. Refrigerate at least 4 hours or overnight until completely set.

Puree 1.5 cups diced mango with sugar and lime juice until completely smooth. Press through a fine-mesh sieve to remove fibers; you should have about 1 cup puree.

Sprinkle gelatin over cold water in a small bowl. Let sit 5 minutes to bloom, then microwave 10-15 seconds until liquid and clear. Whisk immediately into the mango puree.

Pour mango mixture over the set cheesecake, tilting the pan to create an even layer. Arrange remaining diced mango on top. Refrigerate 30 minutes until topping is set. Run a thin knife around the edge before releasing the springform.