Context for Zenock: Alma emphasizes that two witnesses had testified of these things, then adds the detail that Zenock was stoned to death, apparently because of the sermon Alma has quoted. I have already described Israel’s theological shift that downplayed and eventually dismissed Yahweh as the Atoning Messiah. (See 1 Nephi, Part 1: Context, Chapter 2, “The Historical Background of 1 Nephi.”) Both Yahweh’s anger and Zenock’s stoning tells us that Zenock’s listeners violently rejected his interpretation, in fact considering him a blasphemer. Leviticus 24:16 dictates: “And he that blasphemeth the name of the Lord, he shall surely be put to death, and all the congregation shall certainly stone him: as well the stranger, as he that is born in the land, when he blasphemeth the name of the Lord, shall be put to death.” Zenos was also slain for his testimony (Hel. 8:19). This was not a popular doctrine in the northern kingdom, which explains Yahweh’s anger at their unbelief.
It seems likely that Zenos and Zenock were reforming prophets, attempting to teach a correct understanding of the Atoning Messiah to a resistant people. It may also explain why our received Old Testament text does not retain their teachings. If they were considered heretical or blasphemous, they would have been suppressed.
This historical context makes it a little easier to understand why the Nephites had such a complete understanding of the Messiah. They had not received a new revelation. Yahweh had sent prophets to teach this understanding to ancient Israel, but their teachings had been rejected and the prophets slain.