This used to work better than it does today due to the rise of very high salaries in the past 30 years. It used to be that very rich people didn't work. Now there are quite a few people who just get paid a ton. Though the question of whether that's properly understood as wages or capital gets blurry.
(Of course, if you work at a salary of $500,000 for a few years you start to accumulate capital pretty quickly, but it would take a lot of saving for investment income to get bigger than your salary.)
Even in medieval and ancient times a certain portion of the very rich people were merchants/bankers/entrepreneurs - though the stereotypical "very rich" of the time is a major landowner, there are even richer-than-whole-empires people like Fugger or Crassus who did work just as much as the founder-owner-CEOs of modern technology megacorps.
(Of course, if you work at a salary of $500,000 for a few years you start to accumulate capital pretty quickly, but it would take a lot of saving for investment income to get bigger than your salary.)