Ramanujan failed out of college because he only cared about math. He was working as a clerk at the Madras Port Trust, filling notebooks with results, when he wrote to G.H. Hardy at Cambridge.
Hardy nearly ignored the letter. Then he looked closer and decided the formulas "must be true, because if they were not true, no one would have had the imagination to invent them."
He went to England, worked with Hardy for five years, got very sick, came home and died at 32. Mathematicians are still working through his notebooks.