I am reading that many famous composers had unfinished symphonies. Maybe this is it. Like Schubert:
One of Schubert’s most popular creations, and the question is usually Why didn’t he finish it?” Scholars disagree, but the reason is certainly not because he died while working on it. He was 25 and had six years to live. During that time, he composed a tremendous amount of music, including acknowledged masterworks like his Ninth Symphony, his three greatest song cycles, the three final string quartets, his C-major Quintet, and stacks and stacks of piano and vocal music. But a look through his catalog also will find that there are fragments galore, numerous other pieces he left incomplete. It seems to be part of the way he worked.