Answering your question goes beyond my area of expertise I'm afraid, but I would just like to add to one one part of it:

It seems like the Nation of Islam and other groups often engage(d) in Holocaust denial and ideas of the Jews being behind the American slave trade

The notion that Jewish people were the driving force behind the slave trade stems today mainly from the 1991 book The Secret Relationship Between Blacks and Jews, which was produced and published by the Nation of Islam. Suffice to say, it's a a hyperbolic anti-Semitic tirade (also, ironically, popular with some white supremacists) that tries to dress itself up as a work of rigorous scholarship, and which has been pilloried by actual historians of slavery (see Eli Faber's Jews, Slaves, and the Slave Trade: Setting the Record Straight for a sound critical refutation). Whilst I can't comment on what factors are at play in Nation of Islam producing such a work, let me just emphasise for the benefit of everyone interested that it is very much a belief without basis in the historical record.