That "so far" being a middle class the envy of the rest of the world which the US threw away to create a new class of oligarch.
"Back at the tail-end of that era, in the early 1960s, America’s richest faced a 91 percent tax rate on income in the top tax bracket."
https://inequality.org/article/tax-the-rich-we-did-that-once...
No other country has 91% taxes and all those who tried dialled it back. India tried it and it was hilariously bad.
Citation needed that it's not a good policy. Parent comment explained why it was good, and your reply is "or perhaps it was actually bad".
There's a simpler explanation as to why it was rolled back: the people with the most money and power didn't like it and wanted it gone, and worked over time to accomplish this.
1. 90% tax is a net good for society but big bad capitalists colluded to reduce it in every country independently
or
2. 90% is actually a bad policy and every country independently adopted against it including Nordic countries, China, India, USA
you decide which one is more likely.
Despite you showing your bias by phrasing option 1 to look childish, I think it's more or less what happened, actually. It doesn't take much "collusion", just greed and short-sighted self-interest from greedy, short-sighted self-interested people with influence to wield.
And you till haven't cited how that 1) this definitely didn't happen and 2) high tax rates in the highest band is a bad idea.