Why someone becomes famous over another is a matter of talent plus circumstances: friends, funding, events, timing, visibility, etc.. there may have been, and I imagine certainly were, more creative or visionary musicians than Beethoven at the time, but a constellation of factors thrust him into the limelight. Once there he becomes an influencer, both shaping the trajectory of derivatives, and positioning himself as a milepost on the main path of history. We look back and see his genius, certainly because it was there, but more importantly because it has been built upon by generations of progeny and conditioned listeners.