It is hard to believe that Japanese are the least traditional people on this planet.
That's not what the graph means. At least 'traditional' does not mean that the country has a wealth of traditions, costumes, festivals, traditional food, and so on. Not al all. If you look at the
description of the chart on Wikipedia, it says that "
Traditional values emphasize the importance of religion, parent-child ties, deference to authority, absolute standards and traditional family values". I think that '
religious' would have been a more accurate single word to encapsulate all this than 'traditional'.
In that regard, Japan is almost certainly the least religious country in the world. The traditional religions are Buddhism and Shintoism (+ Confucianism if you could it as a religion), neither of which have gods in the sense of Judeo-Chrirstians, Muslim or even Hindu people understand the word. Buddhism is an atheistic philosophy, and even as a philosophy it is almost dead in Japan. Shintoism has 'spirits of Nature', but these aren't gods. They have no name and no particular power or personality. They are just there around. But hardly anybody believes in them anymore. I have lived 4 years in Japan and took every opportunity I could to conduct my own 'anthropological' surveys. I asked people what their religion were. The answer was typically nothing or Buddhist. When I asked which of the 12 Japanese schools of Buddhism they or their family belonged to, half didn't know, and most of the others hesitated and gave me an answer like 'I think Jodoshu, but I have to ask my parents or grandparents'. Can you imagine any Westerner not knowing if their family is traditionally Catholic or Protestant or Orthodox?
In terms of morals, Japanese people are very relativistic. The Japanese are so flexible in their beliefs that I am not surprised that Christianity never took root there, despite numerous attempts since the 16th century. The Japanese aren't even attached to their own culture and tradition, contrarily to popular beliefs in the West. I don't know if you saw
that post of mine where I explain how the Japanese readily threw away a big chunk of their own culture and traditions to adopt Western ways in the late 19th century. I think it is still the only country in the world that became Westernised on its own.
All this together is why I think it is very suitable for Japan to be at the top of the chart (least religious/traditional).