How much do our physical attributes affect our life trajectory? Are beautiful people more successful because they are beautiful? Is there more to it than that?
Without having any data either to inform my response, I think your analysis is compelling, just based on my own experience and observations. The "Matthew Effect" is real! As you note, the feedback loop is comprised of both external influences and one's internal response, meaning reductionist analyses that focus on only one of these factors is necessarily incomplete and misleading, though at least a focus purely on internal factors, while naive, is not disempowering, the way a focus on purely external factors is. The problem seems to be that absent good guidance, people form their habitual internal response very early in life, well before they develop the wisdom and self-awareness to shape these habits consciously. But it's better late than never, when it comes to developing the understanding and maturity needed for improving our default responses.