In a large mixing bowl, combine the instant vanilla pudding mix and the crushed pineapple, including the juice. Stir until the mixture is smooth and well blended.

Add the chopped strawberries, mini marshmallows, and half of the maraschino cherries to the pudding mixture. Gently fold these ingredients in until evenly distributed.

Incorporate the chopped walnuts or pecans into the mixture, stirring until combined.

Carefully fold in the thawed whipped topping until no streaks remain, creating a light and fluffy texture.

Gently add the sliced bananas, being cautious not to mash them. Fold them in until they are evenly mixed without losing their shape.

Drizzle the chocolate syrup over the top of the fluff and gently mix to create swirls throughout the dessert.

Transfer the Banana Split Fluff to a serving dish or individual cups. Top with the remaining maraschino cherries for a decorative touch.

Chill the dessert in the refrigerator for at least one hour before serving, allowing the flavors to meld.