Jacob 1:9

Now Nephi began to be old, and he saw that he must soon die; wherefore, he anointed a man to be a king and a ruler over his people now, according to the reigns of the kings.

Nephi was getting old. He knew he would die soon. So he chose a man to be king and ruler over his people.

Nephi was getting old and knew his time was short. So he anointed someone to be king and rule over the people. That’s how the line of kings began.