@bwenyenye; Karume did NOT make his wealth by selling charcoal, NO!!!
He started by selling charcoal and then moved to other things slowly... 60-odd years later, he is now worth billions.
The fellows you mention who have been selling charcoal since you "were small" have no business being in business! Their failure should not be used as proof that one cannot start with charcoal and become a billionaire. That argument is illogical: it is like saying that no one can pass KCPE simply because no one in your village has ever passed!
Nothing is real unless it can be named; nothing has value unless it can be sold; money is worthless unless you spend it.