Japan's economic growth started well before World War 2. In fact, Japan wouldn't have been able to fight WW2 against the US for so long if it wasn't a fully industrialized country by that time. The country was devastated after the war (just as Germany was), but it wasn't starting from scratch. Many (if not most) of the large Japanese manufacturing conglomerates of today have been successful zaibatsu before the war, that have been only partially broken down and restructured as keiretsu.

I think it's a compelling story to see Japan, the Asian Tigers (two of them former colonies of Japan, the other two former British colonies) and China as having the same growth story, but I don't think it's the same story in all of these places. Outside commentators love to bring up Confucianism, but Confucianism (just like Christianity or Buddhism) is a pretty ancient philosophy and religion that have seen many iterations and has taken many different, perhaps even contradictory shapes and forms over the years. A certain version of it was extremely influential in Japan during the Edo period, but a modern Japanese would probably cite Confucius directly less than a culturally Chinese person would do. And it's certainly an influence in Japan, but the culture is just so different than China, which had its own local influences (including decades of Communism and a not-so-minor Cultural Revolution which targeted the "Four Olds").

I think the best explanation is that all of these countries (in their respective growth period!) had a good degree of political stability and achieved the necessary level of education. They all exercised government guidance through export-oriented policies, but left enough leeway for private companies to choose their own way (in other words, a heavy dose of government meddling that would make neoliberals blush, but not a full-on command economy). And most of all, the timing was right. These countries started to grow their industry (or rebuild it and re-orient it towards export in Japan's case) while fertility was still high and they were relatively poorer than the countries which bought up their goods. And of course, this all happened while world was rapidly globalizing.

It's easy to miss the complex factors involved and recommend the export-oriented playbook to countries where it won't fit, or to think that the same playbook would work forever. It's also easy to blame culture when the things fail. Within Japan, you'd find many commentators who believe the attitudes during the Showa era (1926-1989) were different and the current generation is just incapable of hard work, innovation or whatever else.

But from all I've read and heard about Showa era businesses, they were far less efficient than current Japanese businesses are. The businesses culture was probably probably less risk-averse, but that aversion is itself partly the result of decades of having a somewhat stagnant economy. My pet theory is that Japan was successful during its economic miracle period DESPITE the vast inefficiencies of its corporate culture. It only had western economies to compete with (the Asian Tigers hadn't started to roar yet and China was still far away from industrialization) and the wages in Japan were initially far lower than in the US. From various productivity metrics inefficiencies in other Western countries probably weren't much different back then (this tracks, since it all happened before the mass digitization of the workplace and government which Japan was late to). and despite management, office work and sales practices being inefficient, Japanese companies (most famously Toyota) have developed innovative methods for increasing efficiency and quality on the factory floor.

Fast forward to the 1990s, and Japan is seeing fierce competition from other cheaper producers on many products even before the baby boomer generation is facing retirement with a shrinking population. During that period rich economies are improving their productivity, while poorer economies can just undercut prices due to cheaper labor. Toyota's innovative manufacturing methods are getting adopted outside Japan as well. Japan still leads in places where it has technology advantages or even just a brand or market capture, but in general competition just becomes a lot harder.

At this point, mature economies can only do so much. No matter what the government and individual corporations do, we cannot expect anything close to the growth rates of the 1950s-1970s again. But inefficiencies are clearly hurting Japanese businesses.