I feel like you're making an argument against your thesis instead of for it (?). With higher risk, you expect higher return... so isn't that another tick against Trump's "success"? His ventures were way riskier than an index fund (see bankruptcies and losses), yet they had a markedly lower return. That means they were not good investments.
Well there are two possibilities: 1) Trump's businesses are lower risk and so the lower realized return is as expected 2) there is significant idiosyncratic risk in a single company which can diversified away with the S&P500 while maintaining the same expected return.
I disbelieve (1) because of his multiple high-profile bankruptcies.
