For we did not follow cleverly devised myths when we made known to you the power and coming of our Lord Jesus Christ, but we had been eyewitnesses of his majesty. — 2 Peter 1:16
Well, I had thought it had been Paul who said that. At any rate, that’s not what happened with the Nation of Islam.
Myths normally occur organically, like dreams. Myths are the dreams of a people. That’s not what happened with the Nation of Islam, either.
Trying to find out specifically why Louis Farrakhan says blacks are the “true Hebrews” is — hard to Google, because so many groups make that claim. I did not come upon a specific answer, but came across some Wikipedia articles that may shed some light.
In a recent three-hour address, Farrakhan exhorted Jews to abandon Talmud and embrace only Torah. That puzzles, in that so much of his own teaching itself defies Torah, as well as science and academic history.
They allege that this individual, an evil black scientist, lived ca. 6,600 years ago, and over a period of 600 years he and his successors genetically engineered all non-black races. They allege that he is the same as the Jacob of the Bible. The white race, in particular, was to dominate the original humans (blacks) for 6,000 years; the end of that domination began in 1914.
The number 6,000 is expedient or facile for several reasons. That is the current earliest limit of any awareness we have of specific human activity, according to science and academic history. Earlier than the most primitive human civilizations; earlier than the stone age. So here is alleged both specific human activity (with no evidence) and highly sophisticated science, before then.
6,000 years ago is also, roughly, the date Torah assigns to Creation. So we have activity alleged before Creation.
As to the Biblical Jacob, orthodox Judaism holds that he lived 1653-1506 BCE. That places the NOI character roughly 2,500 years off.
According to the Nation of Islam, the Tribe of Shabazz was the only survivor of thirteen tribes that lived on earth 66 trillion years ago. After a rogue scientist blew up the planet, splitting off the moon, the other tribes perished. The Tribe of Shabazz relocated to the rich Nile valley of Egypt and the present seat of the Holy City, Mecca, Arabia.