The ones parading around with Muslim names and professing a belief in Mohammed (Elijah, not the original) are just ignorant. And desiring to stay that way. They have rage and anger and need an outlet, so they let the Grima Wormtongues lead them to the promised land. Except like all race hucksters, they never seem to arrive. For the work of a tour guide is done when the tour is over, so they make sure it never ends.
Some actually do explore their roots (as Alex Haley did) to find out the truth. Most are just not going to bother with it since it does entail a lot of work (for anyone. not just blacks). It is always easiest to believe in fairy tales than to learn the truth.