How do you prevent mangoes from being eaten by predators?
Put nets or plastic sheets over the trees during the day
While eagles are considered avian apex predators (they are at the top of their food chain) and do not have natural predators, they can be eaten by other carnivores and omnivores (humans, lions, bobcats, cougars, etc.) when they die. Baby eagles are vulnerable and susceptible to being eaten by snakes as well.
You can put a high fence around the tree or patch that covers the top of the plant, or you can buy deer off at a store that works for pests like deer, squirrels, skunks, opossums, and sometimes even small bear, but it doesn't work for birds. You could try going online or using things outside to make to use as a repellent.