This has nothing to do with horses and steel - those have been done to death. These are theological/ideological anachronisms. Just as with technology, new ideology just doesn't appear in a vacuum. It evolves over time, in a particular time and place.
https://www.churchofjesuschrist.org/stu ... 7?lang=eng
2 And it came to pass that he began to preach among the people, and to declare unto them that there should be no Christ. And he preached many things which were flattering unto the people; and this he did that he might overthrow the doctrine of Christ.
So this Sherem guy is supposed to be a staunch Law of Moses orthodox New World Jew, but for some reason he's opposed to the idea that the Messiah would come? First off, there was no messianic expectation at the time to begin with, in the sense of a Messiah who would be rescuing anyone - that developed after the Babylonian captivity, in the old world. For a Hebrew at this time, saying a messiah would come would be no more controversial than saying a high priest or king would come.
And he labored diligently that he might lead away the hearts of the people, insomuch that he did lead away many hearts; and he knowing that I, Jacob, had faith in Christ who should come, he sought much opportunity that he might come unto me.
The notion of "faith in Christ" (faith in the anointed King of Israel) is a entirely anachronistic to the Judaism of the time. The messiah wasn't there to have faith in him, that wasn't the point at all.
And he was learned, that he had a perfect knowledge of the language of the people; wherefore, he could use much flattery, and much power of speech, according to the power of the devil.
This idea of Satan as an evil cosmic force in opposition to God would be anachronistic for the time. That didn't come until 300-200 BCE in the Old World.
And it came to pass that he came unto me, and on this wise did he speak unto me, saying: Brother Jacob, I have sought much opportunity that I might speak unto you; for I have heard and also know that thou goest about much, preaching that which ye call the gospel, or the doctrine of Christ.
Again the "gospel" of the messiah wouldn't have made any sense in this time period.
7 And ye have led away much of this people that they pervert the right way of God, and akeep not the law of Moses which is the right way; and convert the law of Moses into the worship of a being which ye say shall come many hundred years hence. And now behold, I, Sherem, declare unto you that this is bblasphemy; for no man knoweth of such things; for he cannot ctell of things to come. And after this manner did Sherem contend against me.
Even Jesus himself didn't advocate for doing away of the law of Moses. These are doctrines that only developed after Jesus - what are they doing here, supposedly 500 years before Jesus?
And I said unto him: Deniest thou the Christ who shall come? And he said: If there should be a Christ, I would not deny him; but I know that there is no Christ, neither has been, nor ever will be.
Again, a devout Jewish person wouldn't be "denying the Messiah" nor would that even be considered a "sin" in Judaism. Sin was about action, not beliefs.
And he spake plainly unto them, that he had been deceived by the power of the devil. And he spake of hell, and of eternity, and of eternal punishment.
None of the concepts here existed in Judaism 500 years before Jesus. Not hell, not eternal punishment, not the devil (in this sense). They just didn't.
It goes on and on and on. It's no wonder the Book of Mormon has never been taken seriously as a historical text. The anachronisms are overwhelming, and obvious when you are primed with even just a bit of pertinent background historical information about the ancient world.