Much of his work was unappreciated when he was alive
Over a thousand musical compositions are credited to Bach during his lifetime. Unfortunately, some of his work was not well received because it was viewed as being out-of-date and the music was only liked by music experts. The people who did so claimed that they did so since they had no other music to listen to. He was the best organist and organ consultant, but creating music was not his strong suit.
Bach's music was rarely played and was never published for many years after his passing. He faded into obscurity because he was seen as an outdated composer.
Felix Mendelssohn received an original manuscript of Bach's St. Matthew Passion from his grandmother in 1823. On March 11, 1829, in Berlin, he chose to perform it and gave a concert performance of it. It was the piece's first public performance in almost a century. As one of the most revered composers of classical music, Bach was propelled back into international prominence as a result of the response, which sparked a rebirth. Felix Mendelssohn resurrected his music. People began to listen to and play many of his songs a century after his passing.