Limiting our scope to just the length of the Book of Mormon, shouldn’t our starting point be that it is unlikely a first-time author like Joseph would have produced such a long book on his own?
In 2021 Kyler Rasmussen analyzed 116 authors with prominent literary works published between 1800 and 1860 and looked:
Just looking at page counts, Joseph Smith was a clear outlier. He was younger than average, had substantially less education than average. Taking that into account, he produced a work far larger than anyone would have guessed (around 531 dense pages).
How could Joseph write a book the length of the Book of Mormon when he “could neither write nor dictate a coherent and well-worded letter”?