Earlier quoted context omitted.
> Perhaps they realised it’s not a good policy? 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.
so it could be two reasons 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.