Albert Einstein (1879-1955) proposed a theory of general relativity in 1915, which built on work he had done in 1905. He won a well-deserved Nobel Prize, but not for his theory of relativity.
Unlike most advances in physics, the theory of relativity was proposed based on mathematical theory rather than observation. The theory rests on two postulates that are difficult to test, and then derives mathematically what the physical consequences should be. Those two postulates are that the speed of light never changes, and that all laws of physics are the same in every (inertial) frame of reference no matter where it is or how fast it is traveling. This theory rejects Newton's view of gravitation and replaces it with a concept that there is a continuum of space and time, and that large masses (like the sun) bend space in a manner similar to a finger depressing an area of a balloon. From this proposed bending of space the expression arose that "space is curved." But experiments later proved that space is overall flat after all.
Einstein's work had nothing to do with the development of the atomic bomb. Nothing useful has even been built based on the theory of relativity. Only one Nobel Prize (in 1993 and not to Einstein) has ever been given that even remotely relates to the theory of relativity. Many things predicted by the theory of relativity, such as gravitons, have never been found despite much searching for them. Many observed phenomenon, such as the bending of light passing near the sun or the advance of the perihelion in the orbit of Mercury, can be also predicted by Newton's theory.
Einstein never accepted quantum mechanics and his theory of relativity conflicts with it.