The best explanation for the pejorative “lazy” is Zeniff’s prejudice, rather than a historical fact.
What about the second adjective, “idolatrous”? This term is a religious designation: someone has abandoned the true God to worship false gods. Because of the inseparable connection between religion and culture in the ancient world, such a turning away is not only a religious but a cultural deviation. When Zeniff describes the Lamanites in the city of Nephi as rejecting belief in the God of Israel, it is a telling judgment upon the many racial/historical Nephites who were now political Lamanites. These Nephites-become-Lamanites have changed their religion as well as their political allegiance. (See “Excursus: Religion of the Nehors,” following Alma 1.)
Zeniff associates the timing of the first attack with the Lamanite desire to conquer the Zeniffites before they became too powerful. This possibility does not seem particularly likely. Twelve years does not seem like an adequate time period for a people, originally seen as no military threat, to become one. Naturally more children would have been born, but young children are not soldiers. The young boys would have become warrior age, but their mature men would have become old. Rather, the only logical way for the Zeniffites to have become militarily stronger in twelve years would have been to attract smaller hamlets into dependent status or forming political alliances with allies. We have no evidence that this, in fact, occurred, or even that Zeniff’s attribution of this motive to the Lamanites is accurate. It is equally likely that the Lamanites, successful in battle against other people who now became tributaries, turned their attention next to the Zeniffites.