Dual records

Regardless of how much or little Nephi and Jacob knew of what would happen with these records they understood that there would be efforts to destroy the records and so they worked to ensure that the two sets of records would be separated. One would follow political lines of authority and the other would follow a family line. Nephi ensured that those lines would be separate by giving the small plates to his prophet brother and the kingdom to someone outside Jacob’s posterity so that even if political leadership followed from father to son the records would be parallel but not in the same hands.

Nephi understood that over time, any line of succession could include unrighteous people so the threat to the record could arise from either internal or external sources.

I don’t know if either brother thought about it but having one record focused on history and the other on prophecy and spiritual matters would also mean that some people might want to destroy the historical record while not caring for the spiritual record while other people might want to remove the spiritual record while not caring about the historical record despite the fact that both records would include the essential information of what needed to be transmitted to future generations.