Did He Leave a Record of His Thoughtfulness?

Symphony as a form captured his imagination, and because he could say anything with it, i think that is the point that he focused on. No opera wos, he alluded to te hint of those elements, ithe no concertos or quartets. It really is just just symphonies,. though, stretching the form to new horizons and some remarkable leader. Do we know why that that was? Did he leave any record of his thoughtfulness? Or was it simply about the time we dud take to compose these pieces relative to how much time he had?