Your source does not seem aware of the history of tax brackets. In Truman's era the top rate started at $100k income and was 90%. Even at $60k it was 80%. Those are figures from 1953, when Truman left office. [1]

This wasn't that big of a deal for the average person at a time when the median salary was somewhere around $3k, but for a person with significant overhead and large, but not enormous, income -- in other words, exactly like Truman -- it was devastating.

[1] - https://taxfoundation.org/data/all/federal/historical-income...