energy - What is the cause of the large damage by atomic bomb?

I recently read in the Feynman Lectures that when the nuclei like that of uranium which are at the crucial level of balance between strong nuclear forces and electrical repulsive forces are taped lightly, they become unbalanced and are broken into pieces. Subsequently, these pieces are very strongly repelled by each other and the energy released by this method is so-called nuclear energy but is actually electrical energy. So I want to ask: is this the cause of large damage caused by atomic bombs or a major portion of the energy released in these explosions are the electromagnetic waves' energy which is due to mass decay?