Nephi brings with him an important set of artifacts from the Old World. They are the plates of brass, the Liahona, and, as will be noted in verse 14, the sword of Laban. These items will form an important set of physical markers of authority. They represent an ancient authority from another land. Such things were respected and expected in the ancient world.
In later Mesoamerican history, leaders of cities in Maya lands would travel to Central Mexico to be endowed with symbols of power from that government. Physical items that were imbued with power through their age or provenance were important supports for rulership. Thus, we will see these items preserved and passed from Benjamin to his son Mosiah as part of the enthronement ceremony (Mosiah 1:16).
It is possible that the possession of these artifacts was one of the reasons that Nephi was accepted as a leader for the new community. Perhaps his skill with metalworking also provided an economic incentive, though that is never clearly stated. The fact that these artifacts rise to the level of specific mention only underscores their importance.
Thus, with the prosperity to feed themselves, and the symbols of rulership, the new community of Nephi “began to prosper exceedingly, and to multiply in the land.”