To me, there are two key themes and one existential question in play in this story. The key themes: Choice. Power. Existential question: Who am I?

Choice: Each of the four primary characters is confronted by a significant life choice.

-- Clay: Become a Muslim or not?

-- Brown: Quit the NFL and pursue acting or not?

-- Cooke: Continue writing pop songs or something of substance?

-- Malcolm X: Continue down a path which could lead to his death (leader of a movement) or not?

The latter is more implied. There are two conversations with his wife, so we know the domestic, "normal" life is a choice Malcolm X could make. But the implication arises more from the other three who have managed to carve financially lucrative careers by being more mainstream.

That leads to the second theme: Power. Clay and Brown exert power in the arena of athletics. Both also have power as well-known public figures (Clay is especially good at this type of empowerment). Cooke understands the power music and performance. All three have power based on economics: money.

Malcolm X comes from an entirely different place when it comes to power: politics. Indeed, he is suspicious of economic power, especially of a Black man making money in a white world.

Choice. Power. One Night in Miami explores both of these themes to depth. Each is reflected in the personal journeys of the four primary characters and their respective character arcs.