you are correct. J Smith was a smart fiction writer who took the themes of his day -- the Baptist idea that there was a "Great Apostasy" and that the Baptists somehow stayed aside from orthodoxy. Then he took the aspects of the Adventists etc. Then he took the British-Israelism which had roots in Calvinism and British Imperial propaganda
He mixed it up with the fascination about Egypt that was just starting (but the hieroglyphs were not deciphered yet) and mixed it all up together and voila!
The professor painted a picture of this period in Upstate NY as being very electric and claimed that if Smith had come 10 years before or after his disclosures the climate would not have supported acceptance of his doctrines.
When questioned concerning the validity of these LSD doctrines, the professor merely laughed and refused to comment. Perhaps that is why the Mormon authorities cooperated in this venture.