While I agree that there are some people who are held back by their views of themselves, I do not think poverty can be regulated to mostly being a mental condition. The sad fact of the matter is that, in the physical world, money and possessions are power, and those who possess the most of it will work to ensure that power remains within their fold and that it has control over those who don't have power. That's how the physical world works. Spiritual, intellectual, and emotional beliefs might not agree with this, are aware that there is more to the world than just these physical desires and needs, but the physical world, the materialistic world, by and large doesn't care about this. And while there is more to us and to all things than materialistic needs, a solid foundation with materialistic needs being met comes before those other needs and desires can begin to be met.

You are correct, to some degree, in stating that there is a tendency for those who are worse off to victimize themselves and develop poor self-esteem. We should help these people to realize that they can do so much more and to get away from a self-defeating mindset. However, this self-defeating mindset and victimization is far from the only thing holding them back, because there are many things in society, especially capitalistic society, that wishes to hold them back. The main power and thing that needs to be present for a capitalistic society to function is that there needs to be a group in society that can be exploited. Without this exploitable group, a capitalistic society can't function. In order to provide the services it demands, there has to be a group that is inherently without and desperate. Understand that communism is not particularly better, and while it functions under the idea that it is revolutionary and freeing for those who are exploited, it really just continues to exploit them all the same.

A self-defeating mentality is prevalent among those who are of lesser means, but to say that this is the only thing keeping them back and that there are no societal structures that do so is fairly false.

You're correct that nature inherently makes us inequal. But it is a sign of human nobility that we strive to make it so that we are equal.