l don't think it's all about trading big or big risks. It's not just risk, but calculated risks. And yes, having the capital is a necessary starting point for big investments and prosperity. The operational word is 'calculated' risk.
Having big capitals and the mindset to select a good asset were you can buy at the right time is what makes one prosper in trading. Risk is part of our life and what the poor see as risk is what the rich see as opportunity.
You are right for all rich people it is an opportunity to us their money and make money from money but it is equally an opportunity for poor as well, if poor people does not have money they can use bounty and signature campaign which gives free earning without any investment but to become good investor everyone will have to take the risk to once invest.