The first Main Idea was "Why did Albert Einstein create the Atomic Bomb?" Albert Einstein made the Atomic Bomb so that the Nazis didn't get to it first, which saved the world from being taken over by Nazis.
The Second Main Idea was "Why was Albert Einstein Famous?" Albert Einstein was famous for his many theories, which kinda explained the universe as we know it, and stopped the Nazis.
The Third Main Idea was "Why was Albert Einstein Considered Stupid in his early childhood?" Albert actually was stupid in his early childhood, only able to speak at the age of 4 years old, but that opinion was quickly changed.
One Legacy Albert left behind was simply how good of a man he was, he had COMPLETELY devoted his life to others. Another Legacy was the Atomic bomb which revolutionized war as we know it.