Why is huge energy released during fission of uranium nuclei?

As a result of the nuclear fission reaction, enormous energy is released. Indeed, for uranium nuclei, the specific binding energy is approximately 7.8 MeV / nucleon. For fission fragments, whose masses are almost half as much, it is about 8.5 MeV / nucleon. The energy difference in the initial and final states of a nuclear reaction is approximately 220 MeV. This energy is released with each fission act of one uranium nucleus. From a practical point of view, the energy released in one act of fission of uranium nuclei is negligible. But if a large number of uranium nuclei are fissioned at the same time, then huge energy is released. For example, if the mass of all uranium nuclei that underwent fission is equal to 1 kg, then the released energy is approximately equal to the energy that can be obtained by burning 2,500 tons of oil (or 3,000 tons of coal).