Jacob begins with some explanation of things that are and are to come. Isaiah was the prophet of the scattering of the northern kingdom, and the predictor of their gathering. Isaiah is adopted as the prophet of the Babylonian scattering and destruction of Jerusalem, with the gathering remaining in the future. Jacob states that revelation has shown him that the predicted destruction of Jerusalem has occurred, the same revealed information that Lehi had stated in his blessings and lectures to his family at the beginning of 2 Nephi.
Jacob is not heavyhanded with the process of likening. Undoubtedly the people have been taught more than once that they are included in the scattering of Israel, since we have seen that as an important theme in 1 Nephi. Thus, Jacob does not spell out that his audience should see themselves as among those to be gathered. They know that, and are using that understanding as part of the way they will liken the information about the future to their current state.
We discover at the end of Jacob’s sermon that this is not being given as encouragement to the faithful, but as an important call to repentance. Some type of communal sin is occurring, and Jacob sees the solution as a proper understanding of the gospel. Therefore, he reiterates the prophecies of the future that Lehi and Nephi had seen. It is virtually certain that Nephi has taught them of this future, particularly the future mission of the atoning Messiah. Jacob reiterates that Jehovah himself would come in the flesh, and that the reception would be that he would be scourged and crucified.
As the audience listened, they had been told to liken this sermon to themselves, and hence they are being obliquely told that in some way, they too have scourged and crucified their God.