Most of the cash-rich people i know are not smart at all. They are just conservative and can withhold themselves from impulse spending, and introverts, so they

Most of the cash-rich people i know are not smart at all. They are just conservative and can withhold themselves from impulse spending, and introverts, so they don't need to spend much to hang out with friends, which allowed them to build decent savings and build passive income (mostly by buying residential and commercial property, while that will be different in developed countries). Most income-rich on the other hand, are smart.