The Nikkei's bad performance over 30 years is mainly due to how incredibly huge the bubble was before it burst. The real estate underlying the Imperial Palace was valued as much as the entire state of California.
The subsequent 30 years look bad, but the alternative was Great-Depression-style deflation, 25%+ unemployment, and potentially societal collapse.
To further agree: in 1990 Japan's GDP per capita was about 40K USD at a time while the US's was a "mere" 22k.
That 40k was a fake, not true in the sense japan was not actually 2x more productive than the US. Instead it was the product of a super massive bubble. It took over a decade for the US to "catch up". To be more honest: it was japan which needed time for reality to catch up to nominal values.
At this point in time the US is now well past Japan in GDP per capita, which frankly makes sense. The US is much more innovative, with creative destruction occurring everywhere.
The subsequent 30 years look bad, but the alternative was Great-Depression-style deflation, 25%+ unemployment, and potentially societal collapse.