Albert Einstein became a genius because in every normal person, that person uses only 10% of their brain in their lifetime. Well, Albert Einstein used 10% of his brain in some time in his life. Then...
Several things. He developed the theory of relativity (E=MC2) and proved it to be true. Next he demonstrated to the president of the US the steps for splitting an atom based on his theory. Then,...
Because of his many contributions to Physics. He is best known for his Theory of Relativity, which proved essential for further developments in Science.