You should read some of the Abraham books that Jerry and Ester Hicks have written. What they say is that it is impossible to make a huge leap in vibrations to help you achieve a better life. Each person does have the power to improve their lives, but they must start from where they are and build. Before you can achieve something, you must first be able to conceive of it as being true for your life.
If you were someone living in the conditions you describe, how could you even envision wealth in the terms we usually associate with it? Without advertising, tV and the internet constantly telling American's what "wealth" is, ie having more and moe possessions, we would probably have a different concept of wealth also.
True wealth has nothing to do with money. To people such as you describe, wealth might be having food to eat at dinner or not seeing your child die from hunger and disease. Money has no meaning in situations such as these.
Perhaps people such as you describe need a prophet or someone to show them a way to a better life. Until they can conceive of it, they may never achieve it.
In the other scenerio you describe, if someone has wealth, then they are killed because of it and someone steals their wealth, how do we not know that this is what they feared would happen? As it says in the Bible "The thing I greatly feared has come upon me." Perhaps it came BECAUSE that is what they feared, so that is what they focused on.
Whatever you focus on grows. For your starving people in Africa, surely this is what they do focus on because it is all they know. A wealthy person may fear losing their wealth, so this is what they focus on.
Donald Trump actually made and lost many fortunes but he was never not wealthy in his thoughts. He knew wealth was possible for him and even losing it several times, didn't take away his thought that he could be wealthy any time he chose. He thought "wealth thoughts" as Harv Ecker says in Secrets of the Millionaire Mind.
We can't know everything so obviously there are no answers to all questions. Perhaps people are starving in Africa to give the rest of us a chance to do good in the world. Perhaps the girls who are going to Oprah Winfrey's school in Africa, were thinking higher vibrational thoughts and so got that chance to be educated.