Michael B. Jordan is the Human Torch for the same reason Steve Harvey is hosting Family Feud.
Its because Family Feud was formerly the whitest television program in existence.
Okay. Now that its up in the air, let me explain. All of Family Feud's previous hosts were white, and most of the families on the show were, in fact, white families. Your average family that would actually watch Family Feud in real life probably looked something like this.
Their bodies were found buried in the backyard. The father is nowhere to be found.
By giving us Steve Harvey, the program successfully A) Gave us a fun and charismatic host that liven things up and B) Made the show more appealing to the average minority family.
Now, lets look at the Fantastic Four. Sure, to your average comic book fan, Marvel's First Family is a classic and endearing team of superheroes. However, to everyone else, the Fantastic Four might as well be this family.
So, by giving us a Human Torch who is a cool black guy, Fox has successfully A) Given us a great and charismatic actor to liven up the franchise and B) Made the movie more appealing to your average minority family.
Fox addressed the whiteness of the Fantastic Four in a much more subtle way for the earlier films: they got Tim Story (Barbershop, Think Like A Man, other black comedies) to direct.